Memory alloy-actuated apparatus and methods for making and using the same

ABSTRACT

Actuator apparatus having a multi-stable element actuated by memory alloy actuating elements. In one embodiment, the multi-stable actuator comprises a bistable (two-state) diaphragm element adapted to alternate between two stable configurations via forces exerted on the diaphragm by more than one memory alloy filaments in response to thermal activation. The bistable diaphragm element is coupled to a magnetic actuator element resident on a dry portion of a valve fitting, while a plunger actuated by the magnetic actuator element is resident on a wet portion of a valve fitting. Methods for making and using the bistable actuator apparatus are also disclosed.

RELATED APPLICATIONS

This application is related to co-owned U.S. provisional patentapplication Ser. No. 61/189,148 filed Aug. 14, 2008 and entitled“Multi-Stable Actuation Apparatus and Methods for Making and Using theSame” as well as co-owned U.S. provisional patent application Ser. No.61/206,883 filed Feb. 4, 2009 of the same title, each of which areincorporated herein by reference in their entireties.

COPYRIGHT

A portion of the disclosure of this patent document contains materialthat is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent files or records, but otherwise reserves all copyrightrights whatsoever.

FIELD OF THE INVENTION

The present invention relates generally to the area of sensors,actuators and switches, and more specifically in one exemplary aspect,to an improved design for and methods of manufacturing and using a anactuator or sensor apparatus which is actuated by a shape memory alloy(SMA) material.

DESCRIPTION OF RELATED TECHNOLOGY

Actuator assemblies are well known in a variety of industries, includingsuch common applications such as wastewater treatment plants, powerplants, manufacturing plants and refineries, irrigation systems, as wellas in certain consumer devices and applications such as common householdappliances like a dishwasher or a washing machine. One common prior artapparatus for actuator-induced movement is a solenoid. A solenoid is adevice that converts energy (e.g. electrical current, fluid pressure,etc.) into a linear actuation. An electromechanical solenoid typicallycomprises electrically conductive windings that are wrapped around amagnetic core. The windings produce a magnetic field when an electricalcurrent is passed through it, thereby inducing the magnetic core tomove. A pilot valve stem or other such parent apparatus is coupled tothe magnet, thereby actuating a parent device. Other types of“solenoids” also exist, such as pneumatic or even hydraulic solenoids.One exemplary application for solenoids is via the integrated use of asolenoid to actuate a valve. These include anything from large, highpressure systems to smaller home or vehicle systems, including e.g.,automatic flush toilets.

Numerous examples of solenoid actuators exist in the prior art. Forexample, U.S. Pat. No. 7,347,221 to Berger, et al. issued Mar. 25, 2008and entitled “SOLENOID VALVE” discloses a valve assembly comprising twovalves and a single solenoid actuator with only one magnetizing coilthat controls both valves. The corresponding magnetic circuit comprisesa yoke with only two pole pieces. The valves are arranged concentric toone another. The valve closing element of the outer valve is connectedto an armature by means of a sleeve. The cup thus formed receives thearmature that is connected to the valve closing element of the innervalve. The pole piece and the armature form a transmission air gapthrough which the sleeve extends. A coupling air gap is formed betweenthe armatures. The an nature and the pole piece form a working air gap.The valves are opened collectively and are able to close independentlyof one another when the coil is rendered currentless.

A common limitation with regards to electromechanical solenoids(particularly those that are used in small or portable consumerapplications such as the aforementioned automatic flush toilets) is thefact that the actuating current is often generated via a series ofbatteries. Such batteries are often arranged in a series configuration,thereby adding the voltage of each cell while maintaining a commoncurrent through each. These solenoid actuators generally havecomparatively large power requirements, and are often inefficient due tointer alia the internal resistance associated with the application of anelectric current across the solenoid coils.

Furthermore, the reliability of prior art solenoid actuators isdependent upon each of the batteries in the aforementioned “series”power source delivering constant power; if any one of the batteriesfalters, the solenoid actuator cannot function since the current path isbroken (i.e., the “dead” cell will not conduct).

In addition to solenoids, actuators can be coupled to so-calledmulti-stability mechanisms in order to assist with actuator assemblyapplications such as valves. Multi-stability refers to the ability of anobject to exist in multiple (e.g., two or more) stable states. Little orno energy is required to maintain an object in any one of the two stablestates of a bistable object. However, activation energy is required forthe object to switch between the two given stable states.

Bistable mechanisms have been utilized for various functions in theprior art, including valves. For example, U.S. Pat. No. 6,959,904 toBeraldo issued Nov. 1, 2005 and entitled “Solenoid valve device of thebistable type, particularly for controlling the supply of water to awashing machine” discloses a device comprising: a solenoid valve of thebistable type controlled by means of an operating winding; a controlcircuit coupled for operation to a power supply source and capable ofsupplying to the operating winding of the solenoid valve a first and asecond current pulse, for opening and closing the solenoid valverespectively; and a detecting and operating device associated with thesaid solenoid valve, capable of detecting a predetermined dangerousoperating condition thereof, and of causing, in such a case, theautomatic reclosing of the valve for cutting off the flow of the fluid.

U.S. Pat. No. 7,331,563 to Biehl, et al. issued Feb. 19, 2008 andentitled “Valve with compact actuating mechanism” discloses a valvehaving a base body with a passage opening, a movable valve member forclosing and opening the passage opening and an actuating mechanism formoving the valve member in order to open the passage opening. Theactuating mechanism has at least two elements made from a shape memoryalloy which are secured to the base body or a carrier body connectedthereto, and can be alternately shortened in the event of thetemperature rising above a threshold temperature and are connected tothe valve member in such a way that the valve member can be moved from aposition on the passage opening into a position alongside the passageopening when one element is shortened on one side and can be moved backinto the position on the passage opening when the other element isshortened on one side.

Shaped Memory Alloy

Similarly, the use of shaped memory alloy (SMA) for various purposesincluding device actuation is also well known. SMA generally comprises ametal that is capable of “remembering” or substantially reassuming aprevious geometry or physical condition. For example, after it isdeformed, it can either substantially regain its original geometry byitself during e.g., heating (i.e., the “one-way effect”) or, at higherambient temperatures, simply during unloading (so-called“pseudo-elasticity”). Some examples of shape memory alloys includenickel-titanium (“NiTi” or “Nitinol”) alloys and copper-zinc-aluminumalloys.

SMAs often find particular utility in a variety of mechanical systems.For example, U.S. Pat. No. 6,840,257 to Dario, et al. issued Jan. 11,2005 and entitled “Proportional valve with shape memory alloy actuator”discloses a proportional valve for controlling the outlet pressure of afluid flowing therethrough. The valve comprises a valve body having aninlet port and an outlet port for the fluid. The valve also has an innerchamber, within which there is formed a valve seat that may be openedand closed variably by a shutter axially movable from and towards thevalve seat. Movement of the shutter is controlled by a shape memoryalloy (SMA) actuating member operating antagonistically to an elasticmember, the temperature of the fluid being lower than the transitiontemperature of the shape memory alloy. The actuating member and theelastic member are connected to the body valve at opposite sidesrelative to the valve seat. A power control circuit is also provided forcirculating an electric current through the actuating member so as toheat the same by Joule effect from a temperature lower than thetransition temperature to one that is higher. At least one vent hole isformed in the valve body for putting a portion of the chamber upstreamof the valve seat into fluid communication with the outside or acollection network. The actuating member is housed in that portion ofchamber corresponding to the inlet port of the fluid, whereby acontinuous flow of fluid around the actuating member is ensured foraccelerating the cooling process. A closed-loop control circuit for thepower control circuit controls the circulating current as a function ofa pressure signal generated by fluid pressure sensing means and in sucha way as to offset the retarding effect produced by the fluid duringheating of the actuating member.

U.S. Pat. No. 6,843,465 to Scott, issued Jan. 18, 2005 and entitled“Memory wire actuated control valve” discloses a memory wire actuatedcontrol valve comprises a memory wire actuator operatively coupled to afluid control valve. The memory wire actuator includes a housing havingan interior cavity enclosing an electrical platform assembly, anactivation wire and a transfer mechanism. The activation wire is formedof a shape memory alloy. The activation wire is electrically connectedto the electrical platform and mechanically coupled to the transfermechanism. The actuator is activated by conducting electrical currentthrough the activation wire causing the wire to contract therebyactuating the transfer mechanism. The transfer mechanism is operablecoupled to the fluid control valve such that actuated and de-actuatingthe transfer mechanism open and closes the valve.

U.S. Pat. No. 7,055,793 to Biehl, et al., issued Jun. 6, 2006 andentitled “Valve with compact actuating mechanism” discloses a valvehaving a base body with a passage opening, a movable valve member forclosing and opening the passage opening and an actuating mechanism formoving the valve member in order to open the passage opening. Theactuating mechanism has at least two elements made from a shape memoryalloy which are secured to the base body or a carrier body connectedthereto, and can be alternately shortened in the event of thetemperature rising above a threshold temperature and are connected tothe valve member in such a way that the valve member can be moved from aposition on the passage opening into a position alongside the passageopening when one element is shortened on one side and can be moved backinto the position on the passage opening when the other element isshortened on one side.

United States Patent Publication No. 20050005980, to Eberhardt, et al.published Jan. 13, 2005 and entitled “Multiway valve” discloses amultiway valve containing a housing having several inlets and outletsand a chamber. Several seats are provided and each is respectivelyassociated with one inlet or one outlet. A closure element is providedwhich can move between the seats and at least one actuator is providedin the form of an element made of a form memory alloy, able to displacethe closure element from one of the seats when heating occurs. A springelement presses the closure element against each respective seat that itengages.

Despite the foregoing wide variety of actuation approaches andconfigurations in the prior art, there remains an unsatisfied need forimproved actuator apparatus that: (i) utilizes a more reliable powersource than a typical “series” battery arrangement, (ii) reduces overallpower requirements for operation, (iii) reduces power necessary forlinear movement initiated by the actuator, and (iv) reduces internalresistance and Ohmic power losses. Ideally, such improved actuatorapparatus would also address an unsatisfied push towards so-called“green” technologies that enable the utilization of other greentechnologies (such as solar power) as well as reduce the volume ofhazardous waste deposited in our landfills by minimizing or eliminatingthe disposal of batteries that contain toxic metals such as lead,mercury and cadmium.

In another aspect, an improved thermal sensor device is needed whichreduces overall power requirements for operation (and for linearmovement of the sensor), and which provides visual or other indicationof its actuation.

SUMMARY OF THE INVENTION

The invention satisfies the aforementioned needs by providing improvedbistable actuator apparatus, as well as methods for making and using thebistable actuator.

In a first aspect of the invention, exemplary actuator apparatus isdisclosed. In one embodiment, the actuator comprises a diaphragm elementcomprising a plurality of stable configurations, a diaphragm biasingelement coupled to at least a portion of the diaphragm element and atleast one alloy filament coupled to the diaphragm biasing element andcomprising a first and second states. The apparatus further is adaptedto, upon the application of energy to the at least one alloy cause thefilament to assume change shape (e.g., contract), thereby causing thediaphragm element to switch from a first of the stable configurations toa second of the stable configurations.

In a second embodiment, the actuator comprises: a multi-stable elementcomprising at least two substantially stable configurations; a shaftassembly configured to be displaced when the multi-stable elementchanges state from a first to a second of the at least twoconfigurations; a memory alloy filament adapted to exert force on themulti-stable element when actuated, the force causing the multi-stableelement to change state from the first to the second configuration; anda divider element that physically separates the shaft assembly from aplunger, the plunger adapted for actuation of a movable element.

In one variant, the divider element separates a dry-side of the actuatorfrom a wet-side of the actuator, the plunger being disposed on thewet-side, and the movable element comprises a diaphragm.

In another variant, the shaft assembly comprises a magnetic element thatinduces movement with regards to the plunger when the magnetic elementis moved. The plunger comprises a plunger assembly, the plunger assemblyfurther comprising a substantially compliant element and a ferromagneticelement.

In another variant, the magnetic element comprises a ring magnet and theshaft assembly further comprises a ring retainer element that retainsthe ring magnet.

In a further variant, the actuator further comprises a housing assembly,the housing assembly comprising two substantially identical housingelements mated to one another. Each of the substantially identicalhousing elements are disposed in a face-to-face orientation and at anoffset angle with respect to one another.

In another variant, the offset angle at least substantially approximatesone hundred and eighty degrees (180°) of offset. The substantiallyidentical housing elements are further held together via a plurality ofterminal pins.

In still another variant, the actuator further comprises pluralityterminal pins, at least a portion of the pins being in mechanicalcoupling with the memory alloy filament. The memory alloy filamentcomprises a ring element that facilitates assembly by fitting over atleast one of the terminal pins, and the shaft assembly comprises a slotthat permits the receipt of the memory alloy filament withoutnecessitating the filament be thread through an aperture.

In another variant, the memory alloy filament is configured to beactuated through the application of electrical current thereto.

In another embodiment of the actuator, the apparatus comprises: awet-side portion, the wet-side portion comprising a plunger element; anda dry-side portion, the dry-side portion comprising: a bistable elementcomprising two substantially stable configurations; a shaft assemblythat is displaced when the bistable element changes state from a firstconfiguration to a second configuration; and a memory alloy filamentcoupled to the bistable element, the filament causing the bistableelement to change state when the filament is actuated.

In one variant, the shaft assembly actuates the plunger element withoutbeing in physical contact with the plunger element. The shaft assemblycomprises a magnetic element that induces movement with regards to theplunger when the magnetic element is moved.

In another variant, the magnetic element comprises a ring magnet, andthe shaft assembly further comprises a retainer element that retains thering magnet. The retainer element is coupled to a shaft element, theshaft element in turn coupled to the bistable element. The bistableelement is disposed within a housing assembly, the housing assemblyadapted so as to apply a hoop stress upon the bistable element.

In another embodiment of the actuator, the apparatus comprises: anactuator shaft assembly coupled to a memory alloy filament; a valvefitting adapted for regulating a fluid that runs there through; and aplunger in communication with the fluid running through the valvefitting. The actuator shaft assembly actuates the plunger via heating ofat least a portion of the memory alloy filament, the actuator shaftassembly not in communication with the fluid running through the valvefitting.

In a second aspect of the invention, methods of manufacturing theaforementioned actuator apparatus is disclosed.

In a third aspect of the invention, methods of using the aforementionedactuator apparatus is disclosed. In one exemplary embodiment, thisincludes methods of using the aforementioned actuator apparatus as apilot valve; i.e., to control a larger or parent valve.

In a fourth aspect of the invention, a bistable assembly is disclosed.In one embodiment, the bistable assembly comprises a mechanical bistablewith central shaft, and two opposing SMA filaments which act uponopposite sides of the shaft so as to change the bistable from one stablestate to the other. The filaments are adapted to utilize electricalcurrent for activation; when one (tensioned) filament is energized, thebistable is pulled into the second stable state, which then tensions theother filament thereby preparing it for energization and state change ofthe bistable back to its original state.

In a fifth aspect of the invention, business methods associated with theaforementioned actuator apparatus is disclosed. In one exemplaryembodiment, the business method comprises selling the bistable SMAactuator apparatus as a replacement part, thereby reducing energy usagein extant valve installations.

In a sixth aspect of the invention, a more power-efficient actuator isdisclosed. In one embodiment, the actuator comprises SMA filaments thatare operated by a parallel-arranged battery power source. Use of thisparallel arrangement in conjunction with the SMA filaments provides ahighly power-efficient actuator which uses several times less power thana corresponding prior art solenoid arrangement. This arrangement is alsomore reliable than prior art series-cell arrangements, since one (ormore) cell failures will not prevent the actuator from operating.

In a seventh aspect, a more cost effective and ecologically friendly(“green”) battery-powered actuator is disclosed. In one embodiment, theactuator utilizes a parallel battery arrangement which will operate evenwith one or more failed batteries. Especially when used in conjunctionthe power-efficient actuator referenced above, this parallel arrangementnecessitates fewer battery replacements during the same period of time,thereby reducing operating costs and producing less ecologicallydamaging waste. In an eighth aspect of the invention, a memory alloyactuated device is disclosed.

In one embodiment, the device comprises a diaphragm element comprisingtwo substantially stable configurations, a shaft adapted to be displacedwhen the diaphragm element changes state from a first configuration to asecond configuration, and a memory alloy filament adapted to exert forceon the diaphragm, the force causing the diaphragm element to changestate from the first to the second configuration. Mechanical reloadingof the shaft is required to cause the diaphragm to change state from thesecond to the first configuration. In one variant, the filament isadapted to be placed under tension or relaxed when the diaphragm changesstate from the first to the second configurations.

In a ninth aspect of the invention, a thermal sensor/indicator isdisclosed. In one embodiment, the thermal sensor/indicator comprises amechanical bistable element with central shaft, and a temperaturesensitive filament which acts upon the shaft so as to change thebistable from a first stable state to a second stable state. Thetemperature sensitive filament is activated when the environment of thethermal sensor/indicator reaches a predetermined temperature. In onevariant, determination of the predetermined temperature is based atleast in part on one or more properties of the filament including, interalia, the thickness of the filament, the number of strands the filamentis composed of, the length of the filament, and the latency associatedwith responding to environmental (e.g., temperature) changes.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, objectives, and advantages of the invention will becomemore apparent from the detailed description set forth below when takenin conjunction with the drawings, wherein:

FIG. 1 illustrates a perspective view of an exemplary actuator assemblymanufactured in accordance with the principles of the present invention.

FIG. 1A is a cross-sectional view of the actuator assembly of FIG. 1taken along line A-A.

FIG. 1B is a top view of the actuator assembly of FIG. 1.

FIG. 1C illustrates a cross-sectional view of the actuator assembly ofFIG. 1 taken along line B-B of FIG. 1B.

FIG. 2 illustrates a front view of a second exemplary actuator assemblymanufactured in accordance with the principles of the present invention.

FIG. 3 illustrates a perspective view of the exemplary actuator assemblyof FIG. 1 with the top cover removed.

FIG. 3A-3J illustrate a top elevational view of various exemplarybistable diaphragm shapes manufactured in accordance with the principlesof the present invention.

FIG. 4 illustrates a side perspective view of a third exemplary actuatorassembly manufactured in accordance with the principles of the presentinvention.

FIG. 4A illustrates a cross-sectional view of the exemplary actuatorassembly of FIG. 4 taken along line 4A-4A.

FIG. 4B illustrates a cross-sectional view of the exemplary actuatorassembly of FIG. 4A taken along the line 4B-4B.

FIG. 5A illustrates a prior art battery power apparatus having four (4)batteries placed in series to operate a solenoid.

FIG. 5B illustrates a battery power apparatus comprising four batteriesplaced in parallel manufactured in accordance with the principles of thepresent invention.

FIG. 6 illustrates an exemplary bistable actuator used in conjunctionwith a switching valve manufactured in accordance with the principles ofthe present invention.

FIG. 7 illustrates a process flow of an exemplary method ofmanufacturing a bistable actuator in accordance with the principles ofthe present invention.

FIG. 8 illustrates a process flow of an exemplary method of operating abistable actuator in accordance with the principles of the presentinvention.

FIG. 9 illustrates a perspective view of an exemplary bistable latchassembly manufactured in accordance with the principles of the presentinvention.

FIG. 9A illustrates a top elevational view of the exemplary bistablelatch assembly of FIG. 9.

FIG. 9B illustrates a perspective view of the exemplary bistable latchassembly of FIG. 9 with the exterior housing removed.

FIG. 9C illustrates a cross-sectional view of the exemplary bistablelatch assembly of FIG. 9 taken along the line 9C-9C.

FIG. 9D illustrates a cross-sectional view of the exemplary bistablelatch assembly of FIG. 9 taken along line 9D-9D.

FIG. 10 illustrates a perspective view of one exemplary embodiment ofthe bistable diaphragm in accordance with the principles of the presentinvention, shown in a preloaded state.

FIG. 10A illustrates a side elevational view of the bistable diaphragmof FIG. 10, shown in an unloaded (flat) state.

FIG. 10B illustrates a top elevational view of the bistable diaphragm ofFIG. 10A.

FIG. 10C illustrates a side elevational view of the exemplary bistablediaphragm of FIG. 10, shown in a preloaded state.

FIG. 10D is a graphical representation of the relationship between forceexerted on the exemplary bistable diaphragm of FIG. 10, and thecorresponding displacement of the center portion of the diaphragm.

FIG. 11 illustrates a perspective view of an exemplary bistable latchassembly utilizing ring assembly connectors.

FIG. 11A illustrates a perspective view of another exemplary ringassembly for use with the bistable latch of the present invention.

FIG. 12 illustrates a perspective view of one embodiment of amagnetically coupled bistable actuator assembly according to theinvention.

FIG. 12A illustrates a perspective view of the underside of themagnetically coupled bistable actuator assembly of FIG. 12 with thevalve fitting removed, thereby exposing the valve diaphragm.

FIG. 12B illustrates a perspective view of the valve diaphragmillustrated in FIG. 12A, removed from the bistable actuator assembly ofFIG. 12.

FIG. 12C illustrates a top elevational view of the bistable actuatorassembly of FIG. 12.

FIG. 12D illustrates a cross-sectional view of the exemplary bistableactuator assembly of FIG. 12C, taken along the line 12D-12D.

FIG. 12E illustrates a perspective view of the adapter bracket for usewith the exemplary bistable actuator assembly of FIG. 12.

FIG. 12F illustrates a cross-sectional view of the adapter bracket ofFIG. 12E taken along the line 12F-12F.

FIG. 12G illustrates a perspective view of the underside of theexemplary bistable actuator assembly of FIG. 12, with the valve fitting,diaphragm, adapter bracket and actuator cover removed.

FIG. 12H illustrates a perspective view of the exemplary bistableactuator assembly as shown in FIG. 12G with the shaft subassemblyfurther removed from view.

FIG. 12I illustrates a perspective view of the exemplary bistableactuator assembly as shown in FIG. 12H with the magnet sleeve furtherremoved from view.

FIG. 12J illustrates a perspective view of the actuator portion of theexemplary bistable actuator assembly of FIG. 12.

FIG. 12K illustrates a perspective view of the bistable spring, actuatorshaft, actuator terminal and SMA wire assembly of the exemplary bistableactuator assembly of FIG. 12.

FIG. 12L illustrates a perspective view of the assembly of FIG. 12K withthe bistable spring removed from view.

FIG. 12M illustrates a perspective view of the spring assembly for theexemplary bistable actuator assembly of FIG. 12.

FIG. 12N illustrates a cross-sectional view of the exemplary springassembly of FIG. 12M taken along the line 12N-12N.

FIG. 12O illustrates a perspective view of the spring assembly of FIG.12M with the top half of the spring assembly housing removed from view.

FIG. 12P illustrates a perspective view of the partial spring assemblyof FIG. 12O with the bi-stable spring removed from view.

FIG. 12Q illustrates a perspective view of the valve fitting of FIG. 12.

DETAILED DESCRIPTION OF THE INVENTION

Reference is now made to the drawings wherein like numerals refer tolike parts throughout.

As used herein, the terms “electrical component” and “electroniccomponent” are used interchangeably and refer to components adapted toprovide some electrical or electronic function, including withoutlimitation, fuses, transformers, filters, inductors, capacitors,resistors, operational amplifiers, transistors and diodes, whetherdiscrete components or integrated circuits, whether alone or incombination. In addition, other ancillary electronic devices such as forexample, so-called EMI shields and the like, which could be consideredpassive in nature, are considered encompassed as possibilities withinthe meaning of this term.

As used herein, the term “filament” refers to any substantially elongatebody, form, strand, or collection of the foregoing, including withoutlimitation drawn, extruded or stranded wires or fibers, whether metallicor otherwise.

As used herein, the term “shape memory alloy” or “SMA” shall beunderstood to include, but not be limited to, any metal that is capableof “remembering” or substantially reassuming a previous geometry. Forexample, after it is deformed, it can either substantially regain itsoriginal geometry by itself during e.g., heating (i.e., the “one-wayeffect”) or, at higher ambient temperatures, simply during unloading(so-called “pseudo-elasticity”). Some examples of shape memory alloysinclude nickel-titanium (“NiTi” or “Nitinol”) alloys andcopper-zinc-aluminum alloys.

Overview

In one aspect of the invention, an improved actuator apparatus isdisclosed. In one exemplary embodiment, the actuator assembly comprisesa multi-stable (e.g., bistable) diaphragm element, at least one alloyfilament, and a biasing element. The biasing element is used to apply aforce on the bistable diaphragm which has at least two stableconfigurations. The application of force by respective alloy filamentscauses the diaphragm to alternate between the two stable configurations.The biasing element exerts forces on the diaphragm via its connection tothe alloy filament(s) which change shape in response to thermalactivation. Movement of the diaphragm causes movement of a magneticelement, which in turn drives the actuation of a shaft via the use of amagnetic field. Utilization of a magnetic field to actuate the shaftpermits physical separation between the shaft and the other mechanicallydriven actuator components, such as for applications where a fluidic(e.g., gas, liquid, slurry, etc.) or pressure boundary, or sealedinterface, is desired.

The actuator assembly may be used for example to control switchedvalves, pilot valves, oxygen valves, and/or temperature-induced shut-offvalves in which it is important to maintain physical separation betweenthe regulated fluid (including liquids and gases) and the mechanicallydriven actuator assembly. As a result of the physical separation,concerns about fluids coming into contact with the actuator assembly orother fluids or materials are obviated. This is particular useful inapplications where fluid contact with the electrical current applied tothe alloy filament is undesirable (for example, in cases where the fluidis flammable or combustible). In addition, the physical separationfurther prevents the mechanically driven components of the actuatorassembly from coming into contact with otherwise corrosive fluids whichmay damage or wear them over time.

Exemplary Embodiments

Exemplary embodiments of the apparatus and methods of the presentinvention are now described in detail with respect to FIGS. 1-9D. Itwill be appreciated that while described primarily in the context of anactuator or pilot used in conjunction with a fluidic (e.g., gas, liquid,vapor, etc.) valve, the invention is in no way limited to valves, andmay be applied to literally any application requiring actuator-inducedmovement of one or more components.

Moreover, it will be appreciated that while the various embodimentsshown and described herein are described with respect to certaindirections or magnitudes (e.g., upward, downward, left right, higher,lower, etc.), these directions and magnitudes are merely exemplary andrelative in nature, and not in any way a requirement in practicing theinvention. For instance, a device which utilizes an “upward” force inone embodiment could simply be inverted, thereby utilizing a “downward”force just as easily.

Bistable Actuator—

Referring now to FIG. 1, an exemplary embodiment of a bistable actuatorassembly 100 is shown and described in detail. As illustrated, thebistable actuator 100 comprises a housing 102, with the housing 102encasing various elements of the bistable actuator assembly 100 asdescribed subsequently herein. The actuator assembly 100 itself may alsocomprise an integral valve 150 as shown.

Referring now to FIG. 1A, a cross-sectional view of the actuatorassembly 100 of FIG. 1 taken along line A-A is shown and described indetail. The actuator assembly 100 comprises at least one alloy filament104, a bistable diaphragm 108, a central rod 106, and a biasing element112. The biasing element is connected to both the bistable diaphragm 108and central rod 106. In one exemplary embodiment, the filaments 104 a,104 b are adapted to, upon thermal activation, change physical shape.This is accomplished via the use of a shape memory alloy (SMA) materialfor the filaments. As illustrated, the filaments 104 are placed withinthe assembly in such a way that their resultant change in shape (i.e.,during thermal activation) causes force to be applied to the biasingelement 112. This force, in turn, causes the diaphragm 108 to changefrom a first stable configuration to a second stable configuration(hereinafter collectively referred to as “bistable configurations”).These alternating bistable configurations actuate the controlled portion116 of the rod 106 within the valve, resulting in at least two distinctstates for the valve (i.e., “open” and “closed”). The bistable diaphragm108 is, in this embodiment, only stable in the two end states, althoughit will be appreciated that devices which have more than two stablestates can be used consistent with the invention (e.g., tristable withthree states corresponding to “open”, “partially open”, and “shut”).

As is best illustrated in FIG. 1A, the actuator 100 preferably comprisestwo shape memory alloy (SMA) filaments 104 a, 104 b. The SMA filaments104 a, 104 b are metal filaments capable of “remembering” orsubstantially reassuming a previous geometry. That is, an SMA filamentcan substantially change its geometry when heat energy is applied to thefilament and subsequently, when the heat energy is removed, the filamentwill cool, returning substantially to its prior shape. These SMA alloysmay comprise, for instance, nickel-titanium (“NiTi” or “Nitinol”) alloysor copper-zinc-aluminum alloys, etc.

In the present invention, the SMA filaments have two states whennon-energized: a preloaded or tensile state and a relaxed or unloadedstate. In the illustrated embodiment, the original preloaded state ofthe SMA filaments is substantially straight (as depicted by filament 104b in FIG. 1A) and the relaxed state of the filaments is generally curvedin nature (as depicted by filament 104 a). When and while thermal energyis applied, the SMA filaments reduce themselves in length or contract.The application of thermal energy may, in one embodiment, beaccomplished by applying a relatively small current through thefilament, thereby heating the filament and altering its shape (length).The distance traveled by the diaphragm 108 during filament heating isreferred to as “stroke” or “stroke distance”, and the force associatedwith the movement or stroke is termed the “stroke force”.

Depending on the type of material used, the SMA filaments used in theillustrated embodiments may have varying degrees of “memory”. Forexample, in one variant, heating of a filament will cause its length tocontract by a prescribed amount (e.g., 4% of total original length), butcooling back to its original temperature does not cause the filament toregain all of its original length, due to imperfect realignment withinthe material at the molecular/atomic level. Rather, a tensile stressmust be applied to allow the material to regain its full originallength. Such alloys are well known to those of ordinary skill, andaccordingly are not described further herein. However, it be appreciatedthat this behavior can be accounted for in the design of the actuatordescribed herein.

The SMA filaments are disposed above and below the diaphragm 108. Theupper 104 a and lower 104 b filaments are each securely attached, attheir ends, to a securing mechanism 114 extending from the walls of adiaphragm retaining element 110. Both the upper and lower filaments 104are routed through the aforementioned biasing element 112, such as viarespective transverse apertures formed therein. As illustrated in FIG.1A, the biasing element 112 protrudes through the diaphragm 108 and isgenerally perpendicular thereto. However, it is appreciated that inalternative embodiments (not shown), the biasing element 112 may merelybe in contact therewith (i.e. on one side or the other of the diaphragm108), or alternatively the filaments can be in direct contact with thediaphragm 108 (thereby obviating at least one side of the bias element112). The upper filament is routed through the portion of the biasingelement 112 extending above the diaphragm 108, while the lower filamentis routed through the portion of the biasing element 112 extending belowthe diaphragm 108.

The securing mechanisms of the upper filament are located on oppositesides (i.e. 180 degrees from one another as measured in azimuth) withrespect to the diaphragm 108. The same is true of the securingmechanisms of the lower filament. This configuration provides a uniformspacing between the filaments 104 on both the upper and lower portionsin a two-filament configuration as shown.

The illustrated filaments generally form a V-type shape or “bow” that isadvantageous because this shape heightens the stroke distance as appliedto the biasing element 112, thereby causing greater pull and/or pushdistance (stroke) for the diaphragm 108, as compared with a parallelshape configuration, as will be discussed more fully below with respectto FIG. 2.

The configuration of the filaments is perhaps better understood withrespect to the cross-sectional view illustrated in FIG. 1C (See FIG. 1Bfor perspective on the relative geometry of the view illustrated). Ascan be seen in FIG. 1C, the top and bottom filaments 104 a, 104 b residein common plane 111 with one another, although this is by no means arequirement. In some embodiments, it may be desirable for the top andbottom filaments to reside in different planes from the perspectiveillustrated in e.g. FIG. 1C.

The stroke force of the filaments 104 a, 104 b caused as the filaments104 change shape (i.e., between de-energized and energized states) isused to pull and/or push the biasing element 112. The distance betweenthe point where the tensioned or preloaded filament 104 b is secured toa securing element 114 and the point where the filament 104 b is securedto the biasing element 112 is smaller when a filament 104 b is energizedthan when the filament 104 is in its de-energized state. Since thefilament 104 b is preloaded or under tension before the application ofelectrical current, the filaments 104 b when energized contracts andpulls on the biasing element 112. As noted previously, the biasingelement 112 is coupled to the diaphragm 108. Therefore, any forceapplied on the biasing element 112 by the stroke of a filament 104 bcauses displacement of the diaphragm 108.

The forces applied to the diaphragm 108 are capable of switching thediaphragm from a first stable state to a second stable state (i.e.bistable actuation). The unique bistable properties of the diaphragm 108advantageously enable the filaments 104 to be maintained in ade-energized state without requiring the application of additionalenergy/electrical current since once the diaphragm passes through one ormore “neutral” or meta-stable states during the foregoing statetransition, the mechanical (potential) energy resident within thediaphragm will cause all further translation of the diaphragm center tothe new (stable) state, and no further force from the SMA filament (andhence electrical current) is required. Thus, when a filament 104 b coolsdown (i.e., when no current is applied), the diaphragm 108 substantiallymaintains the state brought about by the last application of current.This underscores a significant attribute of the illustrated embodiment;i.e., that once the aforementioned “meta-stable” state (which may or maynot be the center point of travel) of the diaphragm is reached,electrical current to the pulling or preloaded filament (filament 104 bin the illustration of FIG. 1A) can be turned off, thereby allowing thefilament 104 b to relax. This saves energy, since: (i) the current canbe turned off earlier (i.e., at the meta-stable state), and (ii) thecurrent need not be applied to keep the diaphragm (and hence valve) inits stable state.

It is also noted that the stored (potential) energy of the bistable whenit is in its meta-stable state is used to advantage in the illustratedapparatus 100. Specifically, the work (energy) provided by the SMA whentensioned and energized is converted to potential energy stored withinthe bistable diaphragm 108 when in the meta-stable state. This potentialenergy is then used to move the diaphragm (and bias element 112, andanything attached thereto) to the other stable state. Hence, themechanical work or energy done by the SMA filament 104 b duringcontraction is largely preserved and converted to useful work.

Moreover, the filament arrangement of FIG. 1A (i.e., two substantiallyopposing filaments 104 a, 104 b) advantageously uses the aforementionedpotential energy stored within the bistable diaphragm 108 to tension theother (de-energized) filament 104 a when the diaphragm changes state.Specifically, the throw or stroke of the bistable diaphragm 108 from onestable state to the other determines the length of the filaments 104 a,104 b, such that when the diaphragm is in one state, one filament istensioned and the other slackened, and vice versa when in the otherstable state. Hence, one filament is always preloaded and ready foractuation (such as via the aforementioned electrical current beingapplied, or via heat from another external source).

In that the SMA filaments 104 a, 104 b of the illustrated embodimenthave only a certain percentage length variation (e.g., 4-5%) betweenenergized and non-energized states, the aforementioned tensioningfeature is also important to be sure that the filaments 104 a, 104 b donot “run out of stroke” before reaching (just past) the meta-stablestate.

Although the embodiment of FIG. 1A illustrates a total of two (2) SMAfilaments 104 in the configuration described above, it is appreciatedthat any number and configuration of SMA filaments 104 a, 104 b may beutilized consistent with the principles of the present invention. Forexample, in another embodiment (not shown), the invention may comprisetwo (2) SMA filaments per side. These SMA filaments may be distributedevenly around the diaphragm (in order to provide a uniform applicationof stroke force); however, this is by no means a requirement. Theutilization of more or less SMA filaments in the “bow” configuration ofFIG. 1A will correspond generally to increased or decreased stroke forcerequirements for the assembly 100.

In another alternate embodiment, the two filaments 104 a, 104 b arereplaced with four (4) shorter filaments (not shown), each attached onone end to the retaining element 110 and on the other end to the biaselement 112.

In yet another embodiment, illustrated in FIG. 2, the filaments areplaced in a parallel configuration (rather than in a V-shape). Each ofthe filaments is then attached to a portion of the biasing element 112.In other words, as shown in FIG. 2, the upper one or more filament(s)104 n will attach to the upper portion of the biasing element 112, andthe lower one or more filament(s) 104 m will attach to the lower portionof the biasing element 112. Alternatively, the filaments may be attachedto a surface of the diaphragm 108 a, 108 b. As described above, thefilaments 104 n, 104 m have two states: one de-energized and the otherenergized. Moreover, the alternate filament tensioning system describedwith respect to FIG. 1A above is utilized, as demonstrated by filaments104 n and 104 m of FIG. 2 respectively. Application of energy to thetensioned filament 104 m will cause the biasing element 112 to pull therod away from the filament 104 n, the latter receiving the tensioningforce as the diaphragm translates to the other bistable state. Aconfiguration such as this one, having multiple parallel (i.e.,longitudinal with respect to the stroke of the bias element 112)filaments 104 n, 104 m results in greater stroke force (the forcegenerated when the filaments 104 change from one to the other shape)than the previously described V-shaped filament 104 configuration;however, there will be less stroke distance associated with the movementof the filaments 104 n, 104 m in such a parallel filament orientation.

It is noted that utilization of parallel filaments 104 n, 104 m, asdiscussed above, enables the overall appearance of the actuator 100 tocomprise a taller, thinner shape, including e.g., a cylinder, square,rectangle, etc. Such a shape may be beneficial in certain applicationssuch as where a taller, thinner (laterally) profile is needed (alongwith less stroke distance/more force on the bias element 112).

It is also appreciated that the SMA filaments may be of varied oruniform thickness. The thickness of SMA filaments is determinative ofthe force associated with the filament's change in length, and with thelength of time (latency) and amount of energy necessary to cause thechange in the filament's length.

Therefore, it is appreciated that a plurality of configurations havingdifferent number and diameter of filaments 104 may be utilizedconsistent with the present invention to provide various desirableeffects. For instance, in one variant, a plurality of small filamentsdisposed substantially in parallel are used to provide both low latencyand high pull force, since (i) the forces of each individual filamentare essentially additive, and (ii) the latency with each individualfilament is low due to its small diameter. This advantageously providesthe same level of force that a larger filament would, but without thegreater latency associated therewith. However, such an arrangementrequires an increase in electrical current over that for a singlefilament, since each individual filament must be actuated.

In another variant, a number of different filaments with differentthicknesses are used in parallel, thereby giving a distribution of forceand latency. In contrast to the variant previously described wherein allfilaments are of the same thickness, this latter variant results in theforce applied by the filament being distributed over time, since eachfilament will contract (assuming the same start time for the applicationof current) over a different period of time, and with a different forcelevel. The time and/or level of applied current can also be adjusted soas to create the desired force/time profile.

Bistable Diaphragm—

The exemplary embodiment of the bistable diaphragm 108 of the device 100of FIG. 1 is best illustrated in FIG. 3. As shown, the bistablediaphragm 108 in this illustrated embodiment generally comprises adisk-shaped entity. As noted previously, the bistable diaphragm 108 isadapted to comprise two stable states and at least one meta-stablestate. The first stable state of the bistable diaphragm 108 is a convexshape (upward) and occurs when the disk, as shown within the actuator100 in FIG. 3, bulges or protrudes in an upward direction. The secondstable state of the bistable diaphragm 108 is a convex shape (downward),and occurs when the disk as shown within the actuator 100 in FIG. 3bulges in a downward direction. These formations are considered stablein nature because no energy is required to maintain the diaphragm 108 ineither of these two states. Energy is required, however, to cause thediaphragm to change between the two states, as previously described.While traversing between states, the meta-stable state(s) is/arereached, which comprise states that while not stable, are effectivelythe transition points between the diaphragm entering one stable state orthe other. Stated differently, when the diaphragm 108 is in one stablestate, it needs to be moved only to just beyond the meta-stable statefor it to change to the other stable state on its own (due to storedpotential energy). It will be appreciated that the diaphragm, dependingon design, may have one meta-stable state (e.g., roughly at thecenterpoint of travel), or multiple meta-stable states (e.g., one foreach direction of travel that are not located at the same point).

The unique shape of the bistable diaphragm element 108 is such that theactivation energy (energy needed to change the state of the diaphragm108 from one stable state to another) is very minimal. This is becausethe shape of the diaphragm 108 is such that after an initial force isapplied (e.g. the stroke force associated with one of the SMA filaments104 a, 104 b) to a diaphragm in a first stable state and the meta-stablestate is reached, the diaphragm 108 will transition into the secondstable state with no additional force applied.

For example, if the diaphragm 108 of FIG. 1A is in a convex upwardconfiguration with the lower filament 104 b having a tensioned state,when energy is applied to the filament 104 b, the filament will contractand cause the highest point of the diaphragm 108 (e.g., the center) tobe displaced toward the lower filament 104 b. As noted above, theexemplary diaphragm 108 has only two stable states: when the center isat the highest (upward) point and when the center is at the lowest(downward) point. Displacement of the center of the diaphragm 108 awayfrom the highest (or lowest) position places the diaphragm 108 in anunstable configuration, the meta-stable state being the unstableconfiguration wherein no further force is required to cause the statetransition.

It is appreciated that the amount of force required to change stateswith the diaphragm 108 may in one embodiment be less than the peak ormaximal stroke force of the SMA filaments 104, thus rendering theoverall system highly power efficient. In other words, the diaphragm 108and filaments 104 a, 104 b may be adapted such that, when in a firststable state, less than the entire amount of force to be exerted by anSMA filament 104 as it is thermally activated is required to place thediaphragm 108 in the unstable “meta-stable” state, thus triggering thereconfiguration of the diaphragm to a second stable state as describedabove, i.e., only a portion of the force an SMA filament 104 may exertis required to cause a change in the state of the diaphragm 108.

For example, given a bistable diaphragm 108 having a total distancebetween its uppermost and lowermost points of 0.12 inches and an SMAfilament(s) 104 a, 104 b adapted to, upon application of sufficientenergy, cause the diaphragm 108 to move the full 0.12 inches, a strokedistance less than the full stroke distance of 0.12 inches is enough tocause the diaphragm 108 to thereafter conform to a stable state. Thefull stroke of the filaments 104 is not required to cause the diaphragm108 to change from one stable state to another. Rather, an applicationof force causing the diaphragm 108 to move at least beyond a meta-stablepoint between the first and second stable states (which may or may notbe the physical midpoint, depending on the design) will be sufficient tocause the diaphragm 108 to move to the next stable state automatically.

Although the embodiment of FIG. 3 gives a circular “wagon wheel” shapedbistable diaphragm element 108, it is appreciated that the bistablediaphragm element 108 of the present invention may comprise any numberof alternative shapes. Various other exemplary bistable 108 shapes aregiven in FIGS. 3A-3L For example, the bistable 108 may comprise a4-sided “star” (FIG. 3A), a rectangle (FIG. 3B, FIG. 3J), a square (FIG.3C), or a parallelogram (FIG. 3D). FIGS. 3E and 3F illustrate that thebistable 108 may also comprise an equilateral triangle or a righttriangle, respectively. The bistable 108 may likewise resemble a deltoid(FIG. 3G). It is further appreciated that the bistable 108 may compriseany shape having one or more straight edges the above being merelyexemplary of a broader range of shapes. Alternatively, the bistable 108may be generally circular in nature such as the ellipse (FIG. 3H) orcircle (FIG. 3I) or other shape resembling a fan, a clover leaf, orhaving “arms”. It is also appreciated that any of the aforementionedshaped bistable diaphragms 108 may be solid in nature or may include oneor more gaps or openings. Other exemplary bistable configuration will bediscussed below with respect to FIGS. 10-10D.

Another alternative embodiment of a bistable actuator assembly 400 isillustrated in FIG. 4. The illustrated embodiment is designed to utilizean elongated rectangular bistable diaphragm 108 such as that given inFIG. 3J discussed above. Utilization of this particular shape ofdiaphragm 108 (elongated rectangular) is useful in giving the bistableactuator assembly 400 a relatively shallow the depth, d, which resultsin a slim profile assembly 400.

FIG. 4A is a cross-section of the “slim” assembly 400 take along line4A. As shown, the bistable actuator assembly 400 generally comprises arectangular bistable diaphragm 108 j, a rectangular biasing element 112j and two upper 104 x and lower 104 y SMA filaments. In much the samemanner as discussed above, the relaxing and contracting of the SMAfilaments 104 x, 104 y causes the bistable diaphragm 108 to changebetween two stable configurations. The change in configuration causes arod element 106 to be displaced thus opening and closing a valveassociated with the actuator 400. Also illustrated in FIG. 4A, thehousing element 110 further comprises a channel 402 within which thebiasing element 112 j is adapted to snugly fit. The channel 402 and/orbiasing element 112 j of the present embodiment may be outfitted withfriction reducing elements so as to enable the biasing element 112 j tomove up and down (given by the arrows A and B) within the channel whencausing the bistable diaphragm 108 j to change configurations.

FIG. 4B is a cross-section of the “slim” assembly taken along line 413.As illustrated, the channel 402 in the housing 110 acts as a keyingfeature which snugly yet slidably accepts the biasing element 112 j,thereby maintaining positive alignment of the diaphragm and filaments.As is also clear from FIG. 4B, the biasing element 112 j is larger atthe channel 402 than the rectangular diaphragm 108 j; thus, the biasingelement 112 j substantially prevents twisting and other deformation ofthe elongated rectangular diaphragm 108 j.

It is appreciated that, although illustrated as a rectangular biasingelement 112 j and rectangular keying channel 402, other shapes may beutilized consistent with the present invention.

Electrical Package—

As noted above, the present invention requires the application of energyto the filaments 104 in order to cause the filaments to change shape(e.g., length).

In the prior art, energy is applied to the solenoid actuator 500 by wayof a number of low-voltage batteries or cells 502 in series, asillustrated in FIG. 5A. As shown in the example of FIG. 5A, the solenoidactuator 500 requires 6.0V of power for functioning. Thus, four (4)+1.5Vbatteries 502 are placed in series and into electrical connection withthe coiled wires of the solenoid actuator 500. The total powerrequirement per cycle of the prior art solenoid actuator 500,P_(prior art), is given as:P=I×V  Eqn. 1P _(prior art)=2.0A×6.0V=12.0W  Eqn. 2In order to provide adequate power to the solenoid actuator 500, each ofthe batteries 502 must produce sufficient voltage. If any one of thebatteries 502 of the series does not apply the appropriate potential(i.e., 1.5V in this example), the solenoid actuator 500 will notfunction.

Referring now to FIG. 5B, an exemplary electrical package 520 for use inthe present invention is shown. As illustrated, the package 520comprises batteries 502 placed in parallel (rather than in the seriesarrangement of the prior art); although shown as four (4) cells 502, theelectrical package 520 may comprise any number of batteries. The +1.5Vbatteries 502 placed in parallel as shown will apply an overall voltageof 1.5V, which produces current (additive in this configuration)sufficient to cause the SMA filaments 104 a, 104 b of the aboveembodiments to change from a relaxed or de-energized state to theircontracted state. The total power requirement per cycle of theelectrical package 520 for use in the present invention, P_(SMA), isgiven as:P _(SMA)=0.5A×1.5V=0.75W  Eqn. 3Hence, a significant reduction in power (P) is achieved using theSMA-based approach of present invention as compared to the prior artsolenoid-based approach. This allows the same four cells used in theprior art solenoid device to last appreciably longer in the parallelSMA-based device of the present invention, thereby: (i) reducingoperating cost per unit time (i.e., less batteries per unit time); (ii)reducing labor costs per unit time (i.e., fewer man-hours forreplacements of the batteries in a given time period); and (iii) makingthe operation of such devices more “green”, since fewer batteries willneed to be disposed of in an ecologically responsible manner.

It will also be appreciated that with respect to items (i)-(iii) above,there is also an implicit benefit accrued; i.e., that maintenance orrepair personnel, when diagnosing a series-arranged actuator failure,may determine that one or more cells are at fault, and replace them enmasse as opposed to replacing only the defective or failed cell.Similarly, in the context of schedule preventive maintenance, anexemplary maintenance schedule may specify replacement of cells everysix months, or when failure of one cells occurs. This approach resultsin cells which have not yet failed being replaced (ostensibly so as toobviate a second and subsequent maintenance calls), which is wastefuland very ecologically unsound since cells with significant remaininglife (i.e., those which did not fail) are disposed of early.

In contrast, by using a parallel configuration as in the presentembodiment, one or more cells can fail while allowing the actuator tocontinue operating, and all the cells will only be replaced when theactuator no longer functions (thereby corresponding to a greater stateof depletion for all of the cells).

Placing the batteries 502 in a parallel configuration also ensuresreliability. Specifically, the actuator will continue to function if upto three of the batteries 502 should lose charge, etc. (assuming a goodstate of charge for the remaining cell). Parallel battery 502configurations further enable the batteries to have extended lives, aseach of the batteries in parallel shares the load applied across itsterminals (i.e., the current is divided among the cells). Perpreliminary evaluations by the inventor hereof, placement of thebatteries in the aforementioned parallel configuration will decrease theinternal battery resistance approximately four (4) times relative to onesingle battery (i.e., to one-fourth), and sixteen (16) times (i.e., toone-sixteenth) relative to the prior art connection utilizing four suchbatteries in series.

As stated previously, the SMA filaments 104 a, 104 b of the presentinvention require energy to cause a change in length. In other words,the application of energy will cause the filaments 104 a, 104 b toshorten. As the energy is removed, the filaments 104 a, 104 b cool andreturn to an elongated state. Energy need only be applied to thefilaments to cause a change in the state of diaphragm 108 as previouslydescribed. After the diaphragm 108 has changed state, the positionand/or relative pull or push of the filaments will not affect thediaphragm 108. The power consumption of the prior art electricalpackage, C_(prior art), and of the electrical package 520 of the presentinvention, C_(SMA), are given below:C=P×T  Eqn. 4C _(prior art)=12.0W×0.03sec=0.36−sec  Eqn. 5C _(SMA)=0.75W×0.10sec=0.075w−sec  Eqn. 6

The energy applied may take the form of battery supplied power (asdiscussed above), or alternatively from a fixed power supply source(e.g., an AC/DC converter, UPS, etc.) or even a solar cell arrangement.It is also appreciated that in another embodiment (not shown), heatenergy may be applied from alternative sources such as via, conductive,convective, or radiated heat transfer (thereby obviating the need forresistive heating of the filament via electrical current).

Alternative Embodiments Switching Valves

The bistable actuator 100 of any of the above embodiments of the presentinvention may, in one embodiment, be used in conjunction with aswitching valve. An exemplary bistable actuator 100 used in conjunctionwith a switching valve 600 is illustrated in FIG. 6.

As illustrated, the rod 106 of the bistable actuator 100 is adapted tobe connected to a flow control element 608. The flow control elementcontrols the flow between any two of a multitude of receiving ports 602of a switching valve via at least one flow opening 606. The embodimentof FIG. 6 illustrates a switching valve having only two (2) receivingports 602 and one delivery port 604; however, the switching valve maycomprise any number of delivery and receiving ports. Thus, the positionof the flow control element 608 with respect to the delivery 604 andreceiving ports 602 will determine to which of the receiving ports 602flow will be allowed. In one embodiment, the flow control element 608(and its openings 606) will be configured such that at any one time flowwill be restricted to one receiving port 602 while permitted to theother receiving port 602. Alternatively, these may be configured toeither restrict or allow flow to both receiving ports 602 a and 602 bsimultaneously. In yet another embodiment, the flow control element 608(and its openings 606), may be configured to permit back flow, i.e.,flow only between the two receiving ports 602.

Pilot Valves—

In yet another embodiment (not shown), the bistable actuator 100 may beused as pilot or control valve for a larger valve. The larger or parentvalve will typically comprise a valve type different from the SMAembodiments described herein, such as, a solenoid actuator. As is wellknown, a pilot valve is a small valve that controls a limited-flow feedin conjunction with a separate valve controlling a high-pressure flow.The pilot valve helps to reducing the pressure differential on thelarger valve (e.g., by equalizing across the two sides of the valvedisc, or allowing the high pressure on one side of the valve to aid inopening the valve by porting it to the low-pressure side), thus enablingthe high pressure valve to be operated with reduced force (and/orenergy) requirements.

Moreover, a pilot valve can be located at a significant distance fromthe main or parent valve if desired, so as to provide enhancedaccessibility and/or personnel safety (e.g., shielding or reducedexposure to heat, chemicals, radiation, etc.), or reduced noise.

Gas Valves—

In yet another embodiment (not shown), the bistable actuator 100 may beutilized in conjunction with the regulation of gases such as, forexample, via the use of oxygen valves. Specifically, the bistableactuator 100 may control the flow of oxygen in e.g., industrialprocesses including the manufacture of steel and methanol (such as foroxyacetylene welding equipment and gas cutting torches). Other exemplaryuses include, valves regulating the flow the liquid rocket propellantsin rocket engines; in medical breathing gas apparatus adapted for bothmedical facilities and at home; for breathing at altitude in aviation,whether in a decompression emergency, or for continual use (such as inthe case of unpressurized aircraft); and in gas blending for creatingdiving breathing mixes such as nitrox, trimix and heliox. It is furtherappreciated that a bistable actuator may be used in valves forcontrolling the flow of other gases as well.

Advantageously, the use of an SMA actuated valve operated by alow-voltage power source (e.g., 1.5 V batteries arranged in parallel,versus e.g., 6V in series) also reduces the chance of explosion whencarrying potentially explosive gases such as oxygen or hydrogen.

Temperature-Induced Shut-Off Valves—

In yet another embodiment (not shown), the bistable actuator 100 of thepresent invention may be used as a temperature-induced shut-off valve.In other words, the bistable actuator 100 may be adapted or use insituations where certain ambient or internal temperatures are indicativeof malfunction or failure. In one example, the bistable actuator 100 maybe used to shut a fuel or gas valve if the temperature of the fuelbecomes too high. According to this embodiment, the actuator 100 may notcomprise an electrical package as discussed above, but rather, the SMAfilaments 104 would be responsive to temperature changes from othersources. Specifically, they would be placed and thermally coupled sothat a given temperature in the fluid would be communicated directly orindirectly to the SMA filaments, thereby inducing their contraction. Forinstance, a small bypass channel for fluid could be run through theactuator so that the heated fluid could heat the actuator (including theSMA filaments); this system could be calibrated so that when the fluidhit a target temperature, the heat conduction/convection/radiation intothe SMA actuator would be sufficient to actuate the value (or pilot),thereby shutting off or initiating flow as desired.

Utilization of the aforementioned bistable actuator assembly 100 as apilot valve for a larger valve, as a gas valve, and/or as atemperature-induced shut off valve provides a low-power requiring and/orconsuming alternative to the solenoid actuators given in the prior art.Also, as is important in critical applications (e.g., those directlyaffecting human health), the bistable actuator assembly 100 andparallel-arranged power source of the present invention has a morereliable power delivery and may function properly when only one batteryof the electrical package 520 is functioning, thereby providing enhancedreliability.

Manufacturing Methodology—

Referring now to FIG. 7, an exemplary method 700 of manufacturing abistable actuator 100 is given.

At step 702, the biasing element 112 is attached to the bistablediaphragm 108. This can be accomplished via any number via any number ofknown mechanical attachment techniques including adhesives, crimping,threading, friction fit, welding or soldering, etc.

Per step 704, the bistable diaphragm 108 is disposed within a diaphragmretaining housing element 110. This includes securing of fixing at leastportions of the edges of the diaphragm 108 to the housing element sothat the bias element 112, under SMA filament force, can deflect thecenter region of the diaphragm, thereby causing it to change state. Inone embodiment, the biasing element is coupled to the rod 106, therebysupporting the assembled bistable diaphragm within the retaining housingelement 110.

At step 706, one end of a SMA filament 104 is coupled to theaforementioned housing element 110. This can be accomplished, in oneembodiment, by securing the SMA filament to the securing mechanism 114via soldering, welding, crimping, adhesives, or the like. It will beappreciated that based on the design and size of the actuator and itsSMA filaments, the secure coupling of the SMA filaments to the housing(or other component(s)) can be critical to the operation of theactuator, since if the SMA filament ends “slip”, the travel or throw ofthe diaphragm 108 may be insufficient to cause a state change. Hence, inone embodiment, strong and unyielding crimps such as those described inco-owned and co-pending U.S. patent application Ser. No. 11/473,567filed Jun. 22, 2006 and entitled “Apparatus and Methods for FilamentCrimping and Manufacturing”, now U.S. Pat. No. 7,650,914, which isincorporated herein by reference in its entirety, although othercrimping and non-crimping techniques may be used consistent with theinvention as well. It is noted that the foregoing referenced crimpingtechnique provides the salient advantage of being able to securelycrimp; i.e., without any significant creep or give, very fine (smalldiameter) filaments, thereby allowing for smaller filaments within theactuator than would otherwise be achievable using conventional fasteningtechniques. In the present context, the use of smaller filaments has adistinct advantage; i.e., the ability to use less electrical power toheat the filament(s), and/or more rapid reaction time for the sameelectrical power, thereby providing a salient improvement over prior artactuators.

At step 708, the second end of the SMA filament is routed through thebiasing element (e.g., aperture) and then attached to a second securingmechanism 114 opposed to the first. The process is repeated for thebottom SMA filament at step 710. As previously described, the lengths ofthese filaments are carefully set so as to place one in tension at alltimes (depending on the position of the bistable diaphragm).

At step 712, an outer housing element 102 is disposed about theapparatus, thereby providing a protective and/or environmental covering.

Referring now to FIG. 8, an exemplary method 800 of operating a bistableactuator 100 is given. As illustrated, the method 800 comprises first,at step 802, providing a bistable actuator 100 having a bistablediaphragm 108 coupled to a biasing element 112 and at least one SMAfilament 104. The bistable diaphragm is adapted to determine theposition of at least one controlled portion 116 via a rod 106, as shownin FIG. 1A. This controlled portion 116 might for example be a diaphragmor valve stem of a pilot valve.

At step 804, the bistable actuator 100 is coupled to a valve or otherdevice to be controlled (e.g., the aforementioned pilot valve).

Per step 806, the SMA filaments 104 of the bistable actuator 100 arethermally activated. The thermal activation of one of the SMA filaments104 a, 104 b causes the biasing element 112 to exert force on thebistable diaphragm 108, thereby causing the bistable diaphragm 108 tochange from a first stable state to a second. The thermal activation maybe the result of the application of heat energy in the form of batterypower (resistive or Ohmic heating), solar power,conduction/convection/radiation from a nearby heat source, etc. Thechange in form of the diaphragm 108 from a first to a second stablestate causes the controlled portion 116 to change from a first positionto a second. For example, one position of the controlled portion 116 isan “open” valve position, and the other a “closed” or shut position.Thus, the activation of one of the SMA filament 104 a, 104 b causes avalve associated with the controlled portion to open or close.

Bistable Latch Assembly—

Referring now to FIG. 9, one embodiment of a bistable latch assembly 900is shown and described in detail. As illustrated, the bistable latchassembly 900 comprises a housing 904, with the housing 904 encasingvarious elements of the bistable latch assembly 900 as describedsubsequently herein. The housing 904 further comprises a centralaperture 903 within which the plunger head 902 of the bistable latchassembly 900 is adapted to slide (discussed in greater detail below).

The housing 904 may also comprise one or more attachment features 905.The attachment features 905 are in one variant adapted to secure theassembly 900 onto other devices and/or assemblies (not shown). While thefeatures 905 illustrated are shown as comprising pins having a centralopening it will be appreciated that other types or shapes of attachmentfeatures 905 may be utilized as well. For example, fasteners, hooks,threaded screws or threaded apertures, cotter pins, C-clips,interference or friction devices, adhesives, etc. may be employedconsistent with the present invention. Alternatively, the attachmentfeatures may be obviated by way of e.g., an external structure (notshown) which receives or clamps onto the housing 904, such as forinstance a component with a recess formed therein which receives thedevice housing 904. Myriad other approaches to securing the device 900in place will be recognized by those of ordinary skill given the presentdisclosure.

FIG. 9A is a top elevational view of the bistable latch assembly 900 ofFIG. 9. As illustrated, the assembly 900 is generally elongated alongone axis (denoted by line 9C-9C) while substantially circular around asecond axis (denoted by line 9D-9D). This shape is generally dictated byor is an artifact of the interior construction of the device (describedin greater detail below), and hence it will be appreciated that manyother exterior shapes and/or internal configurations can be usedconsistent with the invention.

Referring now to FIG. 9B, the internal components of the bistable latchassembly 900 are illustrated. In the embodiment of FIGS. 9-9D, theassembly 900 comprises a single alloy filament 908, a bistable diaphragm912, held by a diaphragm retaining feature 911, a plunger 909, and twofilament securing mechanisms 906. If desired, two (or more) filamentsmay be used instead of the unitary filament illustrated in FIG. 9B,although this unitary approach provides several benefits includingsimplicity, reduced number of securing mechanisms 906, and highreliability.

The filament securing mechanisms 906 secure two ends of the unitaryfilament 908 to the diaphragm retaining feature 911, such that thefilament 908 generally crosses the length of the bistable diaphragm 912.This can be accomplished via soldering, welding, crimping (such as viamethods described in co-owned and co-pending U.S. patent applicationSer. No. 11/473,567, now U.S. Pat. No. 7,650,914, previouslyincorporated herein), adhesives, or the like. The foregoing crimpingtechniques have the distinct advantage of having extremely low give or“creep” with respect to the filament, which allows the filament to beshorter than it would otherwise need to be if techniques with more creepwere utilized.

Moreover, these crimp techniques also advantageously allow for thecrimping of very small diameter filaments, thereby economizing onfilament material, and allowing the device to react faster than it wouldwith a thicker filament. Specifically, a thinner diameter filament heatsfaster (whether by virtue of electrical current, ambient environment, orotherwise) than one of greater diameter, thereby causing a change in itslength more rapidly.

In the illustrated embodiment, the bistable diaphragm 912 is generallycircular; thus, the filament securing mechanisms 906 are placed acrossthe diameter of the diaphragm 912 from each other, thereby causing thefilament 908 to traverse the length of the bistable 912. The bistable912 of the present embodiment is generally similar to the bistablediaphragm 108 discussed above with respect to FIGS. 1-8. Alternativebistable 912 shapes and placement of filament securing mechanisms 912will be discussed in greater detail below.

The plunger 909 is generally comprised of a head 902 and body 910. Asthe filament 908 crosses the length of the bistable 912, it is fedthrough a cavity 914 in the plunger body 910. In one exemplaryembodiment, the alloy filament 908 comprises SMA and is adapted to, uponactivation, change physical shape. Activation of the SMA filament may bethermal activation (such as via a change in the environmentaltemperature) or application of a conductive, convective or radiative(e.g., IR) heat source, and/or an electrical current. In one exemplaryembodiment, a 0.4 A current may be applied for an impulse duration of0.075 sec. from a 3 Vt power supply to provide sufficient activation(heating) of the filament to cause it to change its physical shape asufficient amount, although it will be appreciated that these values aremerely illustrative of one embodiment.

During the impulse, the SMA wire shrinks, and moves the plunger 909upward. In other words, the change of the physical shape of the filament908 causes upward force to be applied to the plunger body 910. Theplunger 909 is attached to the bistable diaphragm 912 (such as viawelding, brazing, threaded fasteners, adhesives, or any number of otherwell known attachment techniques), and moves up approximately half ofthe stroke from the force imparted by the “shrinking” SMA wire 908. Thisproduces a force on the bistable 912 which causes it to, similar to thediaphragms discussed above, change from a first to a second stableconfiguration. The plunger 909 is carried the remaining half stroke ofvia potential energy accumulated by the bistable element 912. Uponcompletion of the stroke, the plunger 909 will be displaced such thatthe head 902 will be received into the central aperture 903 of theassembly housing 904, and protrude above the plane of the housing 904 asdemonstrated in FIG. 9.

The bistable diaphragm 912, as noted previously, is adapted to comprisetwo stable states and at least one meta-stable state; the two stablestates coinciding with the substantially concave and substantiallyconvex dispositions of the diaphragm, respectively.

The diaphragm 912 is held within the assembly 900 by a diaphragmretaining feature 911. The diaphragm retaining feature 911 maintains thegeneral position of the diaphragm 912 with respect to the assembly 900as the plunger 909 is displaced, while still permitting it to transitionbetween the two stable states. In the illustrated embodiment, thediaphragm retaining feature 911 comprises an upper portion 911 a andlower 911 b portion adapted to at least partly surround the diaphragm912. It is further appreciated that the bistable diaphragm 912 maycomprise any number of various shapes and/or sizes including thosediscussed above with respect to FIGS. 3A-31, those having one or moregaps or being substantially solid in nature. For example, the diaphragm912 may, in one embodiment, be substantially rectangular in nature (suchas that discussed above with respect to FIG. 4) thereby giving theassembly 900 a “slim” appearance. It is further noted that alteration tothe size and/or shape of the bistable diaphragm 912 will necessitatealterations to the position of the filament securing mechanisms 906 andthe diaphragm retaining feature 911. For example, if the bistable 912 ismodified to be rectangular in shape, the securing mechanisms 906 may beplaced near the center point of two opposing sides (either the long orshort side) or alternatively, may be placed at opposite corners of thediaphragm 912. The diaphragm retaining feature 911 is also modified togenerally match the shape of the diaphragm 912 (i.e., is madesubstantially rectangular) in this embodiment.

The filament 908 is disposed substantially above the diaphragm 912. Theconfiguration of the filaments 908 is more clearly illustrated in thecross-sectional view illustrated in FIG. 9C. As illustrated, thefilament 908 generally forms a V-type shape or “bow” so as to produce astrong pull on the diaphragm 912 when the filament 908 changes shape. Asnoted previously, the filament 908 is tensioned or at least partlypreloaded so that, upon thermal activation, the filament 908 willcontract thus pulling on the plunger 909 and forcing the bistable 912 tochange states. Too much “slop” in the tension of the filament may causethe filament to assert insufficient force/throw on the plunger, therebyfailing to cause the bistable to reach the meta-stable state (andsubsequently transition to the other or actuated stable state).

As noted above, the diaphragm 912 is adapted to switch between a firstand a second stable state. The filament 908 need only pull the diaphragm912 through a meta-stable state and mechanical (potential) energyresident within the diaphragm 912 will cause the diaphragm 912 totransition to the new (stable) state.

The cross-sectional view of FIG. 9D illustrates the positioning of theplunger 909 in the “latched up” position. The latched up position occurswhen the bistable 912 has assumed a second configuration due to the pullof the heated filament 908. The second configuration, as noted above,causes the head 902 of the plunger 909 to slide within the centralaperture 903 of the housing 904 and extend upward, so as to beexternally visible, or actuate a switch or other apparatus (if desired).

The diaphragm 912 will remain “latched up” until the assembly 900 isreloaded. In other words, the plunger 909 will remain protruding abovethe plane of the housing 904 until outside force is exerted on theplunger head 902. Reloading occurs when a mechanical force is exerted onthe plunger head 902 inward toward the diaphragm 912 (direction given byarrow D), such as by an operator pressing down on the bead with theirfinger, or an external mechanism. The downward or resetting forceexerted causes the diaphragm 912 to assume a meta-stable state. Asdiscussed above, only approximately one half of a full stroke isrequired to place the diaphragm 912 into a meta-stable state; then thepotential energy of the diaphragm 912 will cause it to transition backto the first stable state (i.e., reloaded state). The application offorce reloads the bistable diaphragm 912 and filament 908, and “latchesdown” the assembly 900. In other words, the plunger head 902 retractswithin the assembly (i.e., no longer protrudes), and the bistablediaphragm 912 is held in the first stable configuration.

As in the embodiments described above, the bistable latching assembly900 of FIGS. 9-9D is advantageously adapted to save energy.Specifically, (i) energy is not required to fully displace the diaphragm(i.e., the diaphragm merely requires power to get from a stable state tothe meta-stable state) and (ii) no power is required to maintain theassembly 900 in the “latched up” or the “latched down” position.

As noted previously, the bistable diaphragm 912 of the bistable latchingassembly 900 may be modified to comprise any number of shapes and sizes,such modification resulting in modification to the overall appearance ofthe assembly 900. For example, the use of a rectangular or squarebistable 912 results in a generally rectangular or square assembly 900.It is further noted that other components of the assembly 900 may bemodified to give a taller, thinner shape (such as modification to theplunger 909, etc.).

It will also be appreciated that a “slim” or reduced profile embodimentof the latch or sensor devices described previously herein may be madeas well; e.g., similar to that of FIGS. 4-4 b described previouslyherein. Such a reduced profile device has certain advantages over theother described embodiments in certain applications, including mostnotably smaller form factor and hence conservation of space.

Activation—

As indicated above, activation of the bistable latching assembly 900requires the input of energy. In one embodiment, the electrical packagediscussed above with respect to FIG. 5B may be used to activate (heat)the filament 908, thereby causing it to change physical shape.Alternatively, other electrical packages may be used (such as thatdescribed in FIG. 5A). In another embodiment, the assembly 900 maycomprise a thermal sensor wherein the filament 908 is activated when theenvironment temperature reaches a particular thermal point. Theparticular thermal point which will activate the filament 908 may bedesigned into the filament including consideration of parameters such asits thickness, whether single or multi-stranded, length, latency ofenvironmental changes (i.e., how long between changes in temperature ofthe environment surrounding the assembly 900 and communication of thischange to the filament sufficient to cause it to actuate, etc.).

Specific Implementations—

The bistable latching assembly 900 of the above configurations may, inone embodiment of the invention, be utilized in conjunction with anydevice which is electronically or electrically opened, such as a cartrunk, car doors, car hood, fuel doors, doors requiring access codes orhaving other security means, etc. Further, the assembly 900 can be usedany number and type of locking and/or unlocking applications, safetydevices, etc. As noted above, in the foregoing applications, theassembly 900 will remain in a “latched down” configuration prior toactivation. One or more control features may, when the assembly 900 is“latched down”, assist in holding the door, hood or trunk closed and/orlocked. Upon activation (either via the thermal characteristics of theenvironment, or via application of a current to the filament 908) of theassembly 900 the control feature(s) will release the door, hood or trunkthus causing the door, trunk or hood to be opened. In one embodiment,the activation of the assembly 900 is regulated by a user's push button,remote, switch, sensor, etc. (i.e., the user presses a button, etc. tocause the assembly 900 to be activated and the door, trunk or hood to beopened). When the user closes the door, trunk or hood the assembly 900will be reloaded to its initial state.

In another embodiment, the bistable latching assembly 900 may be coupledto a mechanism for capturing and/or utilizing energy. For example, theplunger head 902 may be coupled to a spring. When the assembly 900 is“latched down” and the plunger head 902 lies within the assembly 900(i.e., does not protrude from the plane of the housing 904), a springcoupled thereto (not shown) is able to maintain an extended position. Asthe assembly 900 is activation and the bistable diaphragm 912 changesstates, the plunger head 902 will be displaced so that it protrudes fromthe assembly 900. The displacement of the plunger head 902 will, inturn, cause the spring to be contracted, thereby capturing the energycreated by the movement of the plunger head 902. The converse may alsobe true if desired, depending on the particular application; i.e., theaforementioned spring may be “loaded” when the door, etc. is closed andthe plunger similarly reloaded as previously described.

In yet another embodiment, the bistable latching assembly 900 may becoupled to an electrical switch. When the assembly 900 is not activated,the switch may be in a first state, and upon activation and displacementof the plunger head 902, the switch may be forced into a second state.For example, the assembly 900 may utilize a thermally activated filament908 which is responsive to the environment temperature. At a certaintemperature, the assembly 900 will be activated and displacement of theplunger 902 may cause a circuit to break thereby disabling a heater.Because the assembly 900 is activated by the environment temperature, auser will be unable to manually reset the assembly until the surroundingtemperature no longer activates the assembly. In other words, a userwill be unable to reconnect the circuit broken by the displaced plungerhead 902 and operate the heater when the temperature remains too high.

In another embodiment, the bistable latching assembly 900 may beutilized as an electromagnetic switch or LVDT (linear variabledifferential transformer). According to this embodiment, the plungerhead 902 is comprised of ferrous material. When the plunger head 902 isdisplaced, it slides relative to energized primary and secondarywindings, thereby creating a differential magnetic field coupling (andvoltage across each of the windings). The differential voltage can beused for any number of functions that will be recognizable by those ofordinary skill, such as for position indication, to trip a hightemperature indicator or alarm, etc. In yet another embodiment, theassembly 900 can be used to activate a limit switch. As is well known inthe electromechanical arts, limit switches are used to make and breakelectrical contacts and consequently electrical circuits. A limit switchmay detect when the plunger head 902 has moved to a certain position. Acertain operation may be triggered when the limit switch associated withthe assembly 900 is tripped.

Manufacturing Methodology—

The bistable latching assembly 900 of the above embodiments may bemanufactured by attaching the plunger 909 to the bistable diaphragm 912.This can be accomplished via any number of known mechanical attachmenttechniques including adhesives, crimping, threading, friction fit,riveting, welding, soldering, etc.

Next, the bistable diaphragm 912 is disposed within the diaphragmretaining feature 911 such that the diaphragm 912 is maintained inposition while still able to change from one stable state to another.

Then, a first end of the filament 908 is secured to the retainingfeature 911 via a filament securing mechanism 906 connected thereto. Asecond end of the filament 908 is then fed through a cavity or conduiton the plunger 909, and secured to a second securing mechanism 906 alsoconnected to the retaining feature 911. Finally, a housing element 904is disposed about the apparatus as needed; the housing provides aprotective and/or environmental covering and is positioned to receivethe head 902 of the plunger 909 in a central aperture thereof. Inembodiments where the external or environmental temperature is importantfor actuation of the device 900, the housing can be made with one ormore apertures (or even obviated) so as to allow for free flow of air(and/or incident electromagnetic/IP radiation).

Exemplary Bistable Diaphragm—

An exemplary embodiment of a bistable diaphragm for use with e.g., theactuator assemblies of FIGS. 1-8, as well as for use in the bistablelatch assembly of FIG. 9, is illustrated in FIGS. 10-10D.

As shown in FIG. 10, the bistable diaphragm 108, 912 generally comprisesa unitary component having a distorted (i.e., non-planar when in acompressed or preloaded state) “disk” shape and made of a somewhatflexible metallic material. In one embodiment, the bistable diaphragm108, 912 is formed of spring steel, however, it is appreciated that awide range of materials may be used to manufacture the bistable,including inter alia, carbon steel, stainless steel, phosphor bronze,beryllium copper, etc. The component (disk) is comprised of a centralring 1004 having, in its center, an opening or aperture 1002. In theembodiments of FIGS. 1-6, a central rod 106 is fed through the opening1002, and a biasing element 112 is attached thereto. In the embodimentsof FIGS. 9-9D, the body 910 of the plunger 909 is passed through theopening 1002. Yet other configurations may be used as well, theforegoing configurations being merely illustrative.

A plurality of radially disposed beams 1006 extend from the central ring1004. The beams 1006 are spaced about the ring 1004 an equal distanceapart from one another. In the illustrated embodiment, six beams 1006are used; however, it will be appreciated that literally any number ofbeams 1006 (i.e., two or more) may be utilized consistent with thisembodiment of the present invention.

It is further noted that: (i) non-equidistant spacing of the beams 1006about the ring 1004; and/or (ii) non-uniform beam structures, may alsobe utilized. As one example, the beams may be “grouped” together intogroups of two or more, the spacing between the beams of a group beingdifferent than the spacing between groups. Alternatively, the beams maybe varied in size, shape, or geometry as a function of their radial orangular (azimuth) position, such as where they become thicker or thinnerin width (w) or thickness (see e.g., dimension “d” on FIG. 10A), oralternate as a function of azimuth. Other configurations employingnon-equidistant spacing and/or beam geometry will also be recognized bythose of ordinary skill given the present disclosure.

As noted previously, the first end of each beam 1006 extends from thecentral ring 1004. At its other end, each beam 1006 terminates at and isattached to a corresponding arc segment 1008. The beams 1006 aregenerally formed so as to intersect the center of the arc segments 1008.The arc segments 1008, when taken together, form a punctuated circularperiphery, which is concentric to the central ring 1004.

The arc segments 108 are punctuated or separated from one another, thusresulting in gaps 1012 formed in the outer circle of the diaphragm 108,912. Furthermore, the individual beam 1006 and arc segment 1008 pairsare separated from one another so as to form apertures or channels 1010between them. This feature allows each beam/segment combination to beindividually articulated with respect to the others (and the centralring 1004).

Referring now to FIG. 10A, a side elevational view of the bistableapparatus 108, 912 of FIG. 10 is shown in its flattened or uncompressed(rest) state. It will be recognized however that, as described ingreater detail subsequently herein, the bistable diaphragm of thepresent invention need not necessarily comprise a planar or flat shapein its relaxed or uncompressed state.

FIG. 10B is a top elevational view of the diaphragm 108, 912 of FIG. 10,shown unloaded (at rest). In the illustrated embodiment, the bistablediaphragm 108, 912 has six (6) beams 1006, each beam having a width (w).In one embodiment, the beams 1006 are 0.055 inches in width, althoughother values may readily be used. As noted previously, between each arcsegment 108 a gap 1012 is formed having a dimension u. In oneembodiment, the gaps 1012 between neighboring arcs 1008 are 0.034inches, yet other values can be substituted.

Each beam 1006 and arc 1008 pair is disposed about the central ring 1004at a predetermined azimuth; the azimuth may be measured by e.g., a polarcoordinate (e.g., θ, not shown) relative to a reference, or an angle (v)created between the center of first and second beams 1006. In oneembodiment, the six beams 1006 are disposed about the central ring 1004every 60° (at centerline), thereby comprising a full circle (360°).However, it is appreciated that an increase or decrease in the number ofbeams 1006 utilized (and other changes, such as use of non-uniformspacing, beam configuration, etc.) will necessitate smaller or largerangles of separation, respectively. For instance, where the beams 1006are non-uniformly disposed about the central ring 1004, the angle ofdisposition between beams 1006 may be non-constant and/or greater orsmaller than the exemplary measurements discussed above.

As is also illustrated in FIG. 10B, the outer edge (A) of the arcsegments 1008 forms a larger circumference circle, and the inner edge(B) of the arc segments 1008 forms a smaller, concentric circle. In oneembodiment, the radius of the larger, outer edge (A) is 0.3805 inches,while the radius of the inner edge (B) is 0.320 inches, as measured fromthe center of the aperture 1002. The same is also true for circlesformed by the inner (C) and outer (D) edges of the central ring 1004. Inone exemplary embodiment, the diameter of inner circle (i.e., the circleforming the central opening 1002) is 0.175 inches (radius=0.0875 in.),while the radius of the circle formed by the outer edge (D) of thecentral ring 1004 is 0.1255 inches.

As illustrated in FIG. 10C, the exemplary bistable diaphragm 108, 912 inits sprung or preloaded state comprises generally a truncated cone (orfrustum) having a circular base and a circular apex (see FIG. 10B).Accordingly, the diameter of the base (i.e., the circle formed by theouter edge (A) of the arc segments 1008) is significantly larger thanthe diameter of the apex (i.e., the circle formed by the outer edge (D),of the central ring 1004). The diameter of the base (x) isrepresentative of the diameter of the circle formed by the outer edge(A) of the arc segments 1008.

The aforementioned “preload” of the diaphragm is accomplished in oneembodiment by constraining the outer circumference (A) of the aresegments within a substantially circular channel or frame having adiameter somewhat smaller than that of the diaphragm in its unsprungstate (e.g., 0.010 in. smaller, thereby achieving the preloaded overalldiameter (x) of approximately 0.75 in. shown in FIG. 10C). This ineffect causes the diaphragm to “bulge” outward at its center (apex) inone direction or the other relative to the centerline plane,corresponding to the two stable states respectively.

Specifically, the illustrated embodiment of the bistable diaphragm 108,912 comprises two stable states, and one meta-stable state, when thedevice is preloaded as just described. In one stable state, thediaphragm 108, 912 is convex or protruding upwards (shown in theillustrated embodiment). In another stable state, the diaphragm 108, 912is concave or protruding downwards (not shown). In the illustratedembodiment, the apex protrudes upwards a distance (y) above the plane ofthe base (here defined as the plane containing the lowest or outer edgeof the arc segments 1008); e.g., 0.056 inches above the plane of thisbase.

The shape of the illustrated embodiment of the diaphragm 108, 912 issuch that after a force is applied to a diaphragm while in a firststable and preloaded state (e.g., at its apex, such as via a rod orstructure disposed within the aperture 1002 and coupled to the centralring), and the meta-stable state is reached and just exceeded, thediaphragm 108, 912 will transition into the second stable state with noadditional force applied. This property has, as previously discussed,significant advantages in terms of energy or power savings. FIG. 10Dgives a graphical representation of the relationship between theapplication of force onto the diaphragm 108, 912 and the displacement ofthe apex (towards and away from the plane of the base); i.e., thedisplacement of the apex between the two stable states.

As illustrated in FIG. 10D, when force is applied to the bistablediaphragm 108, 912 in a first stable state, the diaphragm is deflectedproportionally until the amount of deflection reaches approximately0.025 inches (the meta-stable state). After the diaphragm 108, 912 hasbeen deflected 0.025 inches, the force required for continued deflectionremains effectively constant until the diaphragm 108, 912 approaches the“snap” position, i.e., the position where the diaphragm 108, 912 changesfrom the meta-stable state to the second stable state (at about 0.065inches of travel), during which no further force need be applied. Thediaphragm apex then settles into the second stable state (at about 0.115in. of displacement). The aforementioned snap is caused by, inter alia,the mechanical forces created within the disk material when the force isapplied (i.e., the work energy of the applied force is converted topotential energy stored within the material structure of the disk whenin the meta-stable state, and then reconverted to work when thediaphragm exits the meta-stable state).

It is noted that in theory, the diaphragm 108, 912 of the illustratedembodiment should change from meta-stable state to the second stablestate the when the diaphragm 108, 912 has been deflected more than 0.056inches. However, in practice it is found that about 0.009 inches ofadditional deflection are needed to achieve the transition. Thediaphragm 108, 912 is able to develop the force profile, shown in FIG.10D (up to 0.750 kilograms force (kgf) in this particular case). Thebistable diaphragm 108, 912 exerts the hysteresis behavior between twostable positions (the curves “Moved Down” and “Moved Up”).

As indicated by the “inverted” data traces given in FIG. 10D, anopposite force is required to transition the diaphragm 108, 912 backfrom the second stable state to the first (e.g., initial position). Thisis effectively symmetric to the first (“normal”) profiles, but in theopposite direction. It is noted that, in an alternative embodiment, abistable diaphragm 108, 912 may not demonstrate a first profiles for thetransition from the first to second state and a second (i.e., notsymmetric) profile for the transition from the second back to the firststate. For example, this asymmetric behavior may cause differentmagnitude of forces or/and deflection when “Moved Down” and/or when“Moved Up”. Asymmetric profiles may result from the use of bistablediaphragm which are not symmetrical in shape, or in instances where thebistable is constrained inside the base or by the symmetrical spokes1006. It is further noted that the graph of FIG. 10D is merelyrepresentative of the displacement/force characteristics of theillustrated embodiment of the diaphragm, and that alternative designconfigurations of the beams will create the different force/displacementprofiles. For example, the use of thicker material may result in aprofile which has greater force “peaks” in both positive and negativedisplacement directions.

As previously referenced, the illustrated embodiment of the bistablediaphragm is manufactured as a single flat structure (which remains flatin its relaxed or unconstrained state). The flat structure is theninserted into a substantially circular containment apparatus. Thecontainment apparatus may comprise for example the housing 102, 904, orthe diaphragm retaining elements 110, 911. As indicated in FIG. 10C, thediameter of the diaphragm 108, 912 is displaced a distance (z; see FIG.10C) when the diaphragm is disposed within the confining shape; thisdisplacement results in the convex or concave overall shape of thediaphragm 108, 912.

It is appreciated that in an alternate embodiment, the diaphragm 108,912 may be formed in the frustum shape at manufacture (i.e., when notpreloaded), and the size of the containment apparatus may besubstantially equal to the diameter of the diaphragm 108, 912 (i.e., thecontainment apparatus may not confine or restrain the diaphragm into asmaller diameter as discussed above).

Such shapes may also comprise a “uni-stable” device; i.e., one wherethere is only a single stable shape, and the meta-stable state must bemaintained by the continued application of force. For instance, theaforementioned filament or SMA wire could be used to maintain a givenforce on the diaphragm (via e.g., the central rod or plunger) while thefilament was heated, but as the heating subsided, the force would berelaxed and the diaphragm would return of its own accord (via thepotential energy stored in the diaphragm material in the meta-stablestate) to the single stable state. This approach obviates the need tomechanically reset the plunger/indicator using an external force, aspreviously described herein.

As illustrated above with respect to the embodiments of FIGS. 1-6 and 9,a rod 106 or plunger 902 is inserted into the central aperture 1002 ofthe diaphragm. The rod 106 or plunger 902 is actuated generallyperpendicular to the planar base of the diaphragm 108, 912 by the SMAwire(s), causing the apex (central ring 1004) of the diaphragm 108, 912to push out towards the confining perimeter (i.e., the walls of thecontainment apparatus). In other words, a pushing or pulling force isapplied to the diaphragm 108, 912 via the rod 106 or plunger 902. Theforce causes the apex (central ring 1004) to be displaced. The circularshape of the diaphragm 108, 912 of the illustrated embodimentadvantageously keeps the rod 106 or plunger 902 in alignment with thecentral opening 1002 and, any other channels provided for the rod 106 orplunger 902. As shown previously in FIG. 10D, the circular shape alsoprovides a particular force profile for the diaphragm 108, 912 throughmuch of its deflection. The outer ring of the diaphragm 108, 912(dimension A formed by the are segments 1008) is separated on thediameter to allow the diaphragm 108, 912 to push against the containmentapparatus to control the force achieved. A single-beam diaphragm (e.g.,a rectangular diaphragm, not shown) may also provide for the pushingforces discussed above; however, such a rectangular diaphragm does notprovide stabilization and alignment (e.g., centralization) of the rod106 or plunger 902.

Filament Securing Mechanisms—

In yet another embodiment, as illustrated in FIG. 11, the securingmechanism 114, 906 used to secure the alloy filaments 104, 908 to theapparatus may comprise an element having an aperture formed therein1100. In the illustrated embodiment, this element 1100 comprises asubstantially ring-shaped portion 1102. The ring 1102 is generallyformed by a frame having the aperture 1103 formed therein. The frame asshown is substantially curved, e.g., rounded; however, it is appreciatedthat the element 1100 may comprise any closed shape. For example, theelement 1100 is, in certain embodiments, generally triangular, circular,elliptical, or square, etc. in shape, depending on the needs of theparticular application.

In the illustrated embodiment, the general shape of the ring 1102 andsize of the aperture formed therein correlate to the shape and size ofthe conductive posts 1108 a, 1108 b over which the rings are inserted.For example, in the illustrated embodiment, the posts 1108 a, 1108 bhave a generally rectangular cross sectional profile (not shown), thusthe aperture of the ring assembly 1100 has a corresponding generallyrectangular shape. However, it is appreciated that the posts 1108 a,1108 b (and aperture of the ring assembly 1100) may comprise literallyany cross-sectional shape. The conductive posts 1108 a, 1108 b of FIG.11 can be adapted to be inserted into an electrical power supply orotherwise conduct electrical current if desired. Because the illustratedposts 1108 a, 1108 b are formed of a conductive material (such as, interalia, metals such as copper or aluminum, metal alloys, etc.), they areparticularly adapted to pass the electric current, as will be discussedherein below.

The ring terminal assembly 1100 further comprises a filament retainingportion 1104. The filament retaining portion 1104 is configured toextend away from the ring 1102 aperture. The filament retaining portion1104 utilizes one or more mechanisms to accommodate at least onefilament 104, 908 (e.g., formed from SMA). In the illustratedembodiment, the retaining portion 1104 accommodates the filaments 104,908 by creating a filament 104, 908 receiving cavity 1106. The cavity1106 is formed by folding a portion of the retaining portion 1104 backover itself. A filament 104, 908 is then received within the cavity1106. In the illustrated embodiment, the filament retaining portion 1104is generally pliable such that the size of the cavity 1106 may beadjusted to easily fit the filament 104, 908. Once the filament 104, 908is received within the cavity 1106, the fold of the retaining portion1104 may be firmly pressed, thereby securing the filament 104, 908therein. It will be appreciated that while FIG. 11 shows a generalizedfilament retaining structure, this portion 1104 may comprise a crimp ofthe type(s) previously described herein if desired; e.g., one adapted tocreate a substantially serpentine channel (cavity 1106), and/or which isparticularly adapted for use with SMA filaments.

The cavity 1106 may be adapted to comprise a grooved or otherwisetextured surface ensuring sufficient electrical contact of the ringassembly 1100 with the filament 104, 908 if required (as well assufficient mechanical strength and advantageous mitigation of any“creep” of the filament within the cavity 1106). The firm contactbetween the cavity 1106 of the ring terminal and the filament 104, 908enables any electrical current passed through the conductive posts 1108a, 1108 b to further pass through the filaments 104, 908. Thus, if avoltage difference is applied between the two posts 1108 a, 1108 b, theinternal resistance of the filament 104, 908 causes the filament 104,908 to heat up and change its length as previously described herein.

In one embodiment, the voltage difference is employed by applying anelectric potential to only one post 1108 a, while the other post 1108 bprovides grounding. In an alternative embodiment, both posts 1108 a,1108 b may be adapted to have electrical potential applied thereto andthe biasing element 112 (or plunger body 910) acts as the ground. Sincethe filament 104, 908 is always in tension there is always a physicalconnection (contact) between the filament 104, 908 and the posts 1108 a,1108 b providing electrical current. The ring terminal assembly 1100eliminates the need for a spring contact or a permanent attachment.

As discussed previously, when heat energy is applied to the filament104, 908, it substantially changes its geometry, which subsequentlycauses a force to be applied to the biasing element 112 (or plunger body910). The force then causes the diaphragm 108 to switch from a firststable state to a second stable state. Accordingly, therein lies yetanother salient advantage of the ring assembly 1100, namely that itallows the ring assembly to pivot such that the entirety of the filamentcan remain directionally pointed at the cavity (e.g. 914, FIG. 9B) asthe biasing element 112 (or plunger body 910) moves thereby minimizingthe stresses that are applied to the filament during actuation. This isparticularly desirable in situations where the size of the filament isrelatively small or otherwise susceptible to breakage by virtue of knownmechanical failure modes such as fatigue or surpassing the yieldstrength of the filament.

It is appreciated that, in embodiments where more than one filament 104,908 is utilized, each filament 104, 908 (i.e., the upper and lowerfilaments in FIG. 11) may be attached via the aforementioned ringterminal assemblies 1100 and respective conductive posts 1108 a, 1108 b.Accordingly, a current may be applied to one of the lower or upperfilament 104, 908 at any one time. For example, when current is appliedto the posts 1108 a, 1108 b associated with the upper filament 104, 908,no current will be applied to the posts associated with the lowerfilament.

The aforementioned embodiments advantageously reduce the complexity andcosts of the apparatus by eliminating the need for a permanent or otherfilament retention feature as well as providing an efficient mechanismfor optionally applying heat energy to the filaments.

Referring now to FIG. 11A, another embodiment of an exemplary ringterminal assembly 1100A is shown. The ring assembly 1100 of thisembodiment comprises a cavity 1106 for receiving and/or crimping afilament 104, 901. The ring portion 1102 is disposed on (and thus inelectrical contact with) the conductive post 1108 c. Although only asingle conductive post 1108 e is illustrated, it will be appreciatedthat an exemplary assembly 100 may utilize more than one such post.

The curved shape of the conductive post 1108 c in the illustratedembodiment enables the ring assembly 1100 to be used in various shapedassembly 100 including, e.g., the assembly illustrated in FIG. 2discussed above. Also illustrated in FIG. 11A, the ring assembly 1100utilizes a screw-in terminal 1110 for receiving a power supplying barrelwire 1112.

Magnetically Coupled Bistable Actuator Assembly—

Referring now to FIG. 12, an exemplary embodiment of a magneticallycoupled bistable actuator assembly 1200 in accordance with theprinciples of the present invention is shown and described in detail.The bistable actuator assembly illustrated in FIG. 12 is adapted for usewith a dual-chamber valve fitting 1296 of the type generally known inthe arts. However, it is recognized that the actuator assembly of FIG.12 can be readily adapted for a variety of different actuatorapplications and/or valve types, such as for example those previouslyset forth herein.

The bistable actuator assembly illustrated in FIG. 12 is coupled to thevalve fitting via an adapter bracket 1210 and a number of fasteningbolts 1288. The adapter bracket illustrated is sized to accommodate thevalve fitting that is desired but can be readily adapted to fit anynumber of different sizes and shapes. One salient advantage (as will bediscussed more fully herein below) is that vast majority of the bistableactuator assembly can be utilized for a wide variety of applicationswith the bulk of the adaptation resulting from only needing to changethe size and dimensions of the adapter bracket. Accordingly, in oneexemplary embodiment, the bistable actuator assembly can utilize customadapter brackets 1210 which permit a single or limited number of SMAactuator assemblies to be utilized with a nearly limitless number ofvalves or other actuated devices, thereby advantageously enabling theSMA actuator assemblies to be utilized with valves or other devices thatwere not otherwise specifically designed for such an application. Forexample, if a user wanted to replace an existing electric solenoidpowered dual-chamber valve with the SMA actuator assembly illustrated inFIG. 12, only the adapter bracket would need to be specifically adaptedfor the prior art electric solenoid dual-chamber valve.

The internal components of the SMA bi-stable actuator assembly 1200 arecovered by the actuator cover 1220 which, in the embodiment illustrated,include four (4) SMA wire terminals 1254 that protrude from the cover.In the embodiment illustrated, a pair of pins would be responsible foractuation of the dual-chamber valve 1296, while the opposing pair ofpins would be responsible for de-actuation of the dual-chamber valve. Inan exemplary embodiment, the respective pairs of pins for each set aredisposed one-hundred eighty (180) degrees from one another as a resultof the geometry of the internal components (see e.g. FIG. 12O). However,it is recognized that the invention is not so limited, and could forexample use any number of external terminal 1254 configurations,placements, etc. In addition, it is recognized that the pins could bereduced in number to three (3) or even two (2) terminals with therouting of current to the respective SMA wires of the actuator assembly1200 being controlled by a decoder circuit of the type well understoodin the electronic arts. In addition, the number of pins could beincreased, should the design for a particular application dictate theuse of SMA wires in the actuation of the actuator assembly.

Referring now to FIGS. 12A-12B, the underside of the actuator assemblyof FIG. 12 is illustrated after removal of the assembly from the valvefitting (so that the diaphragm 1298 can be seen in detail).Specifically, the diaphragm 1298 is utilized to control the movement offluid in the valve fitting. The diaphragm 1298 (FIG. 12B) comprises asealing surface 1273 which sits within a respective cavity of theadapter bracket 1210. The diaphragm also includes a fluid receivingcavity 1271 comprising a plurality of holes 1293 that permit the passageof fluid to/from an external chamber of the valve fitting (1299, FIG.12Q) and a dimple feature 1295 resident within the cavity 1271 thatcomprises a respective aperture 1291 for the passage of fluid to/from aninternal chamber of the valve fitting (1297, FIG. 12Q). Accordingly, thebistable actuator assembly, in the illustrated embodiment of FIG. 12,acts in a similar fashion as a widely known diaphragm valve.

Referring now to FIGS. 12C-12D, the internal components of the bistableactuator assembly are illustrated. Specifically, FIG. 12D illustrates across-sectional view of the actuator assembly taken along lines 12D-12Das shown in FIG. 12C. FIG. 12D illustrates all of the major componentsfor use with the exemplary embodiment of the bistable actuator assemblythat are described in detail more fully herein with respect to FIGS.12E-12Q. As can be seen in FIG. 12D, the actuation mechanism of theactuator assembly 1200 includes the spring assembly housing 1252,terminal pins 1254, bi-stable spring 1256, and actuator shaft 1258. Theactuation mechanism drives the shaft subassembly which includes a ringmagnet 1242 and a ring retainer 1244 which acts to move the ring magnetup and down. As the ring magnet 1242 moves, it drives the plungersubassembly which includes a steel rod 1234, plunger tip 1236 and magnetsleeve 1232. The plunger tip 1236 engages the diaphragm 1298 whichallows fluid to selectively pass or not pass through the valve fitting1296.

Referring now to FIGS. 12E-12F, the adapter bracket 1210 for use withthe bistable actuator assembly 1210 is illustrated. The adapter bracket1210 possesses advantages over other prior art approaches in that, interalia, the adapter bracket allows for the separation of the actuationmechanism resident on the dry-side 1214 of the adapter bracket from thewet-side 1212 in which the fluid that flows through the valve fitting isin contact. It will be appreciated, however, that the actuationmechanism could feasibly be flipped so that it is intentionally withinthe “wet side” (which may be desirable for e.g., temperature/coolingpurposes, lubrication, etc.). The adapter bracket of FIGS. 12E-12Fcomprise two main cavities on the wet-side 1212 of the adapter bracket.The first cavity 1218 is shaped to accommodate and house the diaphragm1298, while the second cavity 1216 is utilized to house the plungerassembly (1230, FIG. 12G) that ultimately interacts with the diaphragmto control the passage of fluids within the valve fitting.

By separating the actuation mechanisms on the dry-side 1214 of theadapter bracket 1210, the reliability of the actuator assembly isimproved. For example, many common issues (such as corrosion,chemical-induced, or thermal-induced degradation) on metal parts thatexist in typical prior art approaches, can be avoided altogether byseparating the actuator mechanism into a dry-side and a wet-side. Inaddition, the costs of the assembly can also be reduced, as moreexpensive corrosion- or environment-resistant components do notnecessarily have to be used since there is no danger of these componentsbecoming exposed to the potentially corrosive fluids traveling throughthe valve fitting. In addition, the risks of electrical shorting andother potential reliability issues or hazard issues (such aselectrocution) can also be further reduced by placing these componentson the dry-side of the adapter bracket.

Referring now to FIG. 12G, the actuation mechanism of the bistableactuator assembly is illustrated in detail. As discussed previously, allof these components (with the exception of the plunger assembly 1230) inthe exemplary embodiment are housed on the dry-side of the adapterbracket. Accordingly, the assembly shown in FIG. 12G is illustrated withthe adapter bracket removed from view so that the internal componentscan be more readily seen. The actuation mechanism comprises three (3)main assemblies: (1) the plunger assembly 1230 that operates on thewet-side of the adapter bracket; (2) the shaft subassembly 1240 thatdrives the plunger assembly 1230 via a magnetic field; and (3) thespring assembly 1250 that drives the shaft subassembly 1240.

The plunger assembly 1230, in the illustrated embodiment, comprisesthree (3) main components, of which only the sleeve 1232 and plunger tip1236 are visible in FIG. 12G. In an exemplary embodiment, the sleeve1232 comprises a ferromagnetic material, while the plunger tip 1236comprises a firm but compliant material (e.g. an elastomeric compound)adapted to seal the nipple aperture 1291 on the diaphragm 1298 (FIG.12B). The shaft subassembly 1240 comprises a ring magnet 1242, whosemovement induces the change in magnetic field that actuates the plungerassembly 1230 and the ring retainer 1244. With respect to the springassembly 1250, only the symmetric housings 1252 and terminals 1254 areclearly visible in FIG. 12G. The remainder of the spring assembly 1250will be discussed further subsequently herein with regards to thediscussion of FIGS. 12H-12P.

Referring now to FIG. 12H, the opposite side of the spring assembly 1250is shown and described in detail. While the ring retainer has beenremoved from view for clarity, the top portion of the actuator shaft1258 can be seen. In addition, the upper SMA wire assembly 1290responsible for pulling the actuator shaft 1258 (as well as the shaftsubassembly 1240) in an upward direction when a current is passed therethrough, is also illustrated. Accordingly, when a current is applied toa respective SMA wire assembly, thereby heating up the respective SMAwire, the ring retainer (not shown) which is actuated by the actuatorshaft shifts the ring magnet 1242 position in an upward or a downwarddirection, thereby actuating the plunger assembly 1230 disposed on thewet side of the adapter bracket.

FIG. 12I illustrates the various components of the plunger assembly withthe magnet sleeve removed from view. Specifically, the magnet sleeve canbe seen to encase the steel rod 1234 which reacts to magnetic fieldinduced by the ring magnet 1242 as well as the plunger tip 1236. Theplunger tip 1236 is the part actually adapted to physically interfacewith the diaphragm (i.e., the nipple portion 1295). In an alternativeembodiment, the steel rod 1234 can be replaced with alternativematerials that alter the magnetic susceptibility of the material used,thereby permitting the plunger assembly 1230 to react more strongly (oralternatively more weakly) to an applied magnetic field (vis-à-vis thering magnet 1242). For example, the steel rod could be replaced with arod comprised of a magnetic material such as neodymium or alnico toprovide more force. Alternatively, the rod could comprise an ironparticle filled plastic that would provide a relatively smaller force.

Referring now to FIGS. 12J-12K, the actuation mechanism comprising thespring assembly, shaft subassembly 1240 and plunger assembly 1230 ismore clearly illustrated. Specifically, the two (2) SMA wire assemblies1290 a, 1290 b can now be seen. In addition, the four (4) terminals 1254illustrated can be thought of us the terminal pairs for each of the SMAwire assemblies 1290 a, 1290 b (i.e., a first pair of terminals 1254acts to apply current through a first of the SMA wire assemblies (e.g.1290 a), while the second pair of terminals 1254 acts to apply currentthrough a second of the SMA wire assemblies (e.g. 1290 b)). Depending onwhich terminal pair has current applied thereto, the actuator shaft 1258will be pulled into one of two directions, thereby placing the bistablespring 1256 into either of its two different bistable states. While theillustrated embodiment shows a pair of SMA wire assemblies thatrespectively pull the shaft in opposing directions, the invention is notso limited. For example, in an embodiment, the actuator assemblyincludes only a single SMA wire assembly (or set of SMA wire assemblies)that only pulls the shaft in a single direction with a return springreturning the bistable spring to an opposing state.

The SMA wire assemblies 1290 of the illustrated embodiment comprise anSMA wire 1292 and a crimp terminal 1294 present at either end of the SMAwire, although it will be appreciated that other approaches may be used.In an exemplary embodiment, the SMA wire comprises a 0.005 inch diameterDynalloy wire. Furthermore, in an exemplary embodiment, the crimpterminals 1294 comprise a ring-like structure with a serpentine likechannel that holds the SMA wire 1292 in place without damaging itExemplary crimp structures useful with the present invention aredescribed in co-owned and co-pending U.S. patent application Ser. No.11/473,567 filed Jun. 22, 2006 and entitled “Apparatus and Methods forFilament Crimping and Manufacturing”, now U.S. Pat. No. 7,650,914, whichwas previously incorporated herein by reference in its entirety. Asalient advantage of the aforementioned ring-like structure is that sucha structure facilitates the manufacture of the spring assembly; i.e.,the SMA wire assembly 1290 can be manufactured separately and simplyinserted over the respective ends of the terminals 1254, thereby easingassembly. In addition, the ring like structure also has an advantage,particularly when used with relatively thin SMA wires, in that it allowsthe crimp terminal 1294 to pivot as the actuator shaft 1258 moves. Thispivoting motion relieves stress at the interface of the SMA wire 1292and the crimp terminal 1294, as the crimp terminal remains aligned withthe SMA wire throughout the travel of the actuator shaft. While aring-like structure is illustrated as being associated with the crimpterminal 1294, it is appreciated that other structural shapes can bereadily substituted while still offering: (1) ease of assembly; and/or(2) the ability to pivot, such as for example C-shaped terminalstructure that partially encircles the crimp terminal or a pin-likestructure that is received within an aperture located on the crimpterminal.

Moreover, the aforementioned crimp elements are highly precise in natureand allow for the crimping of very fine gauge SMA filaments withoutsignificant creep, thereby allowing for inter alia reduced powerconsumption and shorter filaments (i.e., less percentage creep allows ashorter filament to be used for the same effective stroke, and theshorter/thinner filament requires less electrical power or heat appliedto actuate the actuator).

Referring now to FIG. 12L, the construction and design of the actuatorshaft 1258 is more readily apparent. The actuator shaft has both anupper 1262 and a lower slot 1264 adapted to receive an SMA wire 1292. Inthe illustrated embodiment, the slots 1262, 1264 of the actuator shaftare shaped so as to permit the SMA wire to be routed through the centerof the shaft without necessitating that the wire be routed through a viahole. This eases assembly by allowing the SMA wires 1292 to be routedonto the actuator shaft after the SMA wire assemblies have beenassembled. The top portion of the actuator shaft is shaped so as to bereceived within a corresponding receptacle on the actuator cover (1220,FIG. 20) such that the actuator shaft can be partially guided by theactuator cover during actuation of the shaft. Furthermore, in anembodiment, retention features 1259 located near the bottom portion ofthe actuator shaft are adapted to receive and secure the ring retainer(not shown).

Referring now to FIGS. 12M-12N, the construction of the exemplaryembodiment of the symmetric housing 1252 is more clearly illustrated.Specifically, as can be seen in FIG. 12N, the housing structure of thespring assembly 1250 is comprised of two (2) identical spring assemblyhousings 1252 that are essentially inverted so that they can be disposedface-to-face and attached so that they are rotated at 180 degrees withrespect to one another (i.e., so that the cantilever snaps 1270 aredisposed at opposite sides with respect to one another). In theillustrated embodiment, the cantilever snaps 1270 from respective onesof the spring assembly housings engage the opposite housing, and helphold the two housings in place together. In addition, in an exemplaryembodiment, the spring assembly terminals 1254 are adapted to bereceived within respective slots on the outer radial portion of theassembled housings 1252. These slots contain features that are adaptedto receive respective features on the spring assembly terminals, andaccordingly fit together in e.g., a press-fit type assembly. Thispress-fit feature helps contain the two housings together afterassembly.

Referring now to FIG. 12O, a perspective view of the spring assembly1250 with the top housing removed from view is illustrated. As can beseen in FIG. 12O, the bistable spring 1256 is received within arespective groove 1259 located within each of the respective housings1252. This groove 1259 is important in that it is sized so as to apply apredetermined hoop stress onto the outer periphery of the bistablespring, thereby enabling its actuation between states. While thebistable spring 1256 is illustrated in a “wagon wheel” type ofconfiguration, it is recognized that other bistable spring geometries(such as those described previously herein) could readily be substitutedin lieu of the configuration illustrated. In an alternativeconfiguration, the bistable spring is designed so that a hoop stressneed not be applied by the housing. Specifically, the bistable spring isstamped such that it projects to one side in its stamped state and cansubsequently switch to an alternative state via the application of force(e.g. via an actuated alloy filament).

It can be appreciated that while certain aspects of the invention havebeen described in terms of a specific sequence of steps of a method,these descriptions are only illustrative of the broader methods of theinvention, and may be modified as required by the particularapplication. Certain steps may be rendered unnecessary or optional undercertain circumstances. Additionally, certain steps or functionality maybe added to the disclosed embodiments, or the order of performance oftwo or more steps permuted. All such variations are considered to beencompassed within the invention disclosed and claimed herein.

While the above detailed description has shown, described, and pointedout novel features of the invention as applied to various embodiments,it will be understood that various omissions, substitutions, and changesin the form and details of the device or process illustrated may be madeby those skilled in the art without departing from the invention. Theforegoing description is of the best mode presently contemplated ofcarrying out the invention. This description is in no way meant to belimiting, but rather should be taken as illustrative of the generalprinciples of the invention. The scope of the invention should bedetermined with reference to the claims.

What is claimed is:
 1. An actuator, comprising: a multi-stable elementconfigured to have at least two stable configurations, said multi-stableelement comprising one or more radially disposed beams extending from acentral ring, said beams coupled to one or more arc segments that form acircular periphery concentric to said central ring; a shaft assemblyconfigured to be displaced when said multi-stable element changes statefrom a first to a second of said at least two configurations; a memoryalloy filament adapted to exert force on said multi-stable element whenactuated, said force causing said multi-stable element to change statefrom said first to said second configuration; and a divider element thatphysically separates said shaft assembly from a plunger, said plungeradapted for actuation of a movable element.
 2. The actuator of claim 1,wherein said divider element separates a dry-side of the actuator from awet-side of the actuator, said plunger being disposed on the wet-side.3. The actuator of claim 2, wherein the movable element comprises adiaphragm.
 4. The actuator of claim 1, wherein said shaft assemblycomprises a magnetic element that induces movement with regards to theplunger when the magnetic element is moved.
 5. The actuator of claim 4,wherein said plunger comprises a plunger assembly, said plunger assemblyfurther comprising a substantially compliant element and a ferromagneticelement.
 6. The actuator of claim 4, wherein said magnetic elementcomprises a ring magnet and said shaft assembly further comprises a ringretainer element that retains said ring magnet.
 7. The actuator of claim1 further comprising a housing assembly, said housing assemblycomprising two substantially identical housing elements mated to oneanother.
 8. The actuator of claim 7, wherein each of the substantiallyidentical housing elements are disposed in a face-to-face orientationsuch that one or more cantilever snaps disposed on each of the housingelements are disposed opposite each other.
 9. The actuator of claim 8,wherein said substantially identical housing elements are further heldtogether via a plurality of terminal pins.
 10. The actuator of claim 1,further comprising a plurality of terminal pins, at least a portion ofsaid pins being in mechanical coupling with said memory alloy filament.11. The actuator of claim 10, wherein said memory alloy filamentcomprises a ring element that facilitates assembly by fitting over atleast one of said terminal pins.
 12. The actuator of claim 10, whereinsaid shaft assembly comprises a slot that permits the receipt of saidmemory alloy filament without necessitating the filament be threadthrough an aperture.
 13. The actuator of claim 1, wherein said memoryalloy filament is configured to be actuated through the application ofelectrical current thereto.
 14. An actuator assembly, comprising: awet-side portion, said wet-side portion comprising a plunger element;and a dry-side portion, said dry-side portion comprising: a bistableelement comprising two substantially stable configurations; a shaftassembly that is displaced when said bistable element changes state froma first configuration to a second configuration; and a pair of opposingmemory alloy filaments routed through said shaft assembly and causingsaid bistable element to change state when said filaments are actuated,where the pair of opposing memory alloy filaments comprises at least afirst memory alloy filament and a second memory alloy filament; whereinthe first memory alloy filament is disposed above said bistable elementand the second memory alloy filament is disposed below said bistableelement.
 15. The actuator assembly of claim 14, wherein said shaftassembly actuates said plunger element without being in physical contactwith said plunger element.
 16. The actuator assembly of claim 15,wherein said shaft assembly comprises a magnetic element that inducesmovement with regards to the plunger when the magnetic element is moved.17. The actuator assembly of claim 16, wherein said magnetic elementcomprises a ring magnet, and said shaft assembly further comprises aretainer element that retains said ring magnet.
 18. The actuatorassembly of claim 17, wherein said retainer element is coupled to ashaft element, said shaft element in turn coupled to the bistableelement.
 19. The actuator assembly of claim 18, wherein said bistableelement is disposed within a groove formed within a housing assembly,said groove sized to apply a predetermined hoop stress upon a peripheryof said bistable element.